Method and apparatus for transmitting and receiving downlink channel

ABSTRACT

The present disclosure discloses a method for receiving a downlink signal by a UE in a wireless communication system. Particularly, the method may include receiving a synchronization signal block (SSB) including a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcasting channel (PBCH), and obtaining an indicator indicating a subcarrier spacing for the downlink channel from the PBCH, and receiving the downlink signal on the basis of the subcarrier spacing. The indicator may indicate a different subcarrier spacing according to a frequency band in which the UE operates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage application under 35 U.S.C. § 371of International Application No. PCT/KR2018/006790, filed on Jun. 15,2018, which claims the benefit of U.S. Provisional Application No.62/544,212, filed on Aug. 11, 2017, and U.S. Provisional Application No.62/521,263, filed on Jun. 16, 2017. The disclosures of the priorapplications are incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to a method and apparatus fortransmitting and receiving a downlink (DL) channel, and moreparticularly, to a method and apparatus for transmitting and receiving aDL channel on the basis of a subcarrier spacing for the DL channel,indicated by physical broadcast channel (PBCH) contents included in asynchronization signal block (SSB).

BACKGROUND ART

As more and more communication devices demand larger communicationtraffic along with the current trends, a future-generation 5^(th)generation (5G) system is required to provide an enhanced wirelessbroadband communication, compared to the legacy LTE system. In thefuture-generation 5G system, communication scenarios are divided intoenhanced mobile broadband (eMBB), ultra-reliability and low-latencycommunication (URLLC), massive machine-type communication (mMTC), and soon.

Herein, eMBB is a future-generation mobile communication scenariocharacterized by high spectral efficiency, high user experienced datarate, and high peak data rate, URLLC is a future-generation mobilecommunication scenario characterized by ultra high reliability, ultralow latency, and ultra high availability (e.g., vehicle to everything(V2X), emergency service, and remote control), and mMTC is afuture-generation mobile communication scenario characterized by lowcost, low energy, short packet, and massive connectivity (e.g., Internetof things (IoT)).

DISCLOSURE Technical Problem

The present disclosure is intended to provide a method and apparatus fortransmitting and receiving a downlink (DL) channel.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

According to an embodiment of the present disclosure, a method forreceiving a downlink channel by a user equipment (UE) in a wirelesscommunication system may include receiving a synchronization signalblock (SSB) including a primary synchronization signal (PSS), asecondary synchronization signal (SSS), and a physical broadcastingchannel (PBCH), and acquiring an indicator indicating a subcarrierspacing for the downlink channel from the PBCH, and receiving thedownlink signal on the basis of the subcarrier spacing. The indicatormay indicate a different subcarrier spacing according to a frequencyband in which the UE operates.

Herein, the indicator may be 1 bit.

Further, if the frequency band in which the UE operates exceeds aspecific value, the subcarrier spacing indicated by the indicator may be60 kHz or 120 kHz.

Further, if the frequency band in which the UE operates is below aspecific value, the subcarrier spacing indicated by the indicator may be15 kHz or 30 kHz.

Further, the downlink channel may carry system information or a messagefor initial access.

Further, a subcarrier spacing for the system information and asubcarrier spacing for the message for initial access may be equal.

According to the present disclosure, a UE for receiving a downlinkchannel in a wireless communication system may include a transceiverconfigured to transmit and receive a wireless signal to and from a BS,and a processor configured to control the transceiver to receive asynchronization signal block (SSB) including a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and a physicalbroadcasting channel (PBCH), to acquire an indicator indicating asubcarrier spacing for the downlink channel from the PBCH, and tocontrol the transceiver to receive the downlink signal on the basis ofthe subcarrier spacing. The indicator may indicate a differentsubcarrier spacing according to a frequency band in which the UEoperates.

Herein, the indicator may be 1 bit.

Further, if the frequency band in which the UE operates exceeds aspecific value, the subcarrier spacing indicated by the indicator may be60 kHz or 120 kHz.

Further, if the frequency band in which the UE operates is below aspecific value, the subcarrier spacing indicated by the indicator may be15 kHz or 30 kHz.

Further, the downlink channel may carry system information or a messagefor initial access.

Further, a subcarrier spacing for the system information and asubcarrier spacing for the message for initial access may be equal.

According to an embodiment of the present disclosure, a method fortransmitting a downlink channel by a BS in a wireless communicationsystem may include transmitting a synchronization signal block (SSB)including a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), and a physical broadcasting channel(PBCH), and transmitting the downlink signal on the basis of asubcarrier spacing indicator transmitted on the PBCH. The subcarrierspacing indicator may indicate a different subcarrier spacing accordingto a frequency band in which a UE operates.

According to the present disclosure, a BS for transmitting a downlinkchannel in a wireless communication system may include a transceiverconfigured to transmit and receive a wireless signal to and from a UE,and a processor configured to control the transceiver to transmit asynchronization signal block (SSB) including a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and a physicalbroadcasting channel (PBCH), and to control the transceiver to transmitthe downlink signal on the basis of a subcarrier spacing indicatortransmitted on the PBCH. The subcarrier spacing indicator may indicate adifferent subcarrier spacing according to a frequency band in which theUE operates.

Advantageous Effects

According to the present disclosure, a DL channel is received on thebasis of a subcarrier spacing for the DL channel, indicated by asynchronization signal block (SSB). Therefore, the DL channel can alsobe received with a different numerology from that of the SSB.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other effects of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the control-plane and user-planearchitecture of radio interface protocols between a user equipment (UE)and an evolved UMTS terrestrial radio access network (E-UTRAN) inconformance to a 3^(rd) generation partnership project (3GPP) radioaccess network standard.

FIG. 2 is a view illustrating physical channels and a general signaltransmission method using the physical channels in a 3GPP system.

FIG. 3 is a view illustrating a radio frame structure for transmitting asynchronization signal (SS) in a long term evolution (LTE) system.

FIG. 4 is a view illustrating an exemplary slot structure available innew radio access technology (NR).

FIG. 5 is a view illustrating exemplary connection schemes betweentransceiver units (TXRUs) and antenna elements.

FIG. 6 is a view abstractly illustrating a hybrid beamforming structurein terms of TXRUs and physical antennas.

FIG. 7 is a view illustrating beam sweeping for a synchronization signaland system information during downlink (DL) transmission.

FIG. 8 is a view illustrating an exemplary cell in an NR system.

FIG. 9 is a view referred to for describing embodiments of multiplexinga primary synchronization signal (PSS), a secondary synchronizationsignal (SSS), and a physical broadcast channel (PBCH) in asynchronization signal (SS).

FIGS. 10 to 14 are views referred to for describing methods forconfiguring an SS burst and an SS burst set.

FIG. 15 is a view referred to for describing a method for indicatinginformation about an SS index and an SS transmission time.

FIGS. 16 to 33 are views illustrating performance measurement resultsaccording to an embodiment of the present disclosure.

FIGS. 34 to 36 are views referred to for describing embodiments ofconfiguring a bandwidth for a DL common channel.

FIG. 37 is a block diagram illustrating components of a transmissionapparatus 10 and a reception apparatus 20, for implementing the presentdisclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

The configuration, operation, and other features of the presentdisclosure will readily be understood with embodiments of the presentdisclosure described with reference to the attached drawings.Embodiments of the present disclosure as set forth herein are examplesin which the technical features of the present disclosure are applied toa 3^(rd) generation partnership project (3GPP) system.

While embodiments of the present disclosure are described in the contextof long term evolution (LTE) and LTE-advanced (LTE-A) systems, they arepurely exemplary. Therefore, the embodiments of the present disclosureare applicable to any other communication system as long as the abovedefinitions are valid for the communication system.

The term, Base Station (BS) may be used to cover the meanings of termsincluding remote radio head (RRH), evolved Node B (eNB or eNode B),transmission point (TP), reception point (RP), relay, and so on.

The 3GPP communication standards define downlink (DL) physical channelscorresponding to resource elements (REs) carrying information originatedfrom a higher layer, and DL physical signals which are used in thephysical layer and correspond to REs which do not carry informationoriginated from a higher layer. For example, physical downlink sharedchannel (PDSCH), physical broadcast channel (PBCH), physical multicastchannel (PMCH), physical control format indicator channel (PCFICH),physical downlink control channel (PDCCH), and physical hybrid ARQindicator channel (PHICH) are defined as DL physical channels, andreference signals (RSs) and synchronization signals (SSs) are defined asDL physical signals. An RS, also called a pilot signal, is a signal witha predefined special waveform known to both a gNode B (gNB) and a UE.For example, cell specific RS, UE-specific RS (UE-RS), positioning RS(PRS), and channel state information RS (CSI-RS) are defined as DL RSs.The 3GPP LTE/LTE-A standards define uplink (UL) physical channelscorresponding to REs carrying information originated from a higherlayer, and UL physical signals which are used in the physical layer andcorrespond to REs which do not carry information originated from ahigher layer. For example, physical uplink shared channel (PUSCH),physical uplink control channel (PUCCH), and physical random accesschannel (PRACH) are defined as UL physical channels, and a demodulationreference signal (DMRS) for a UL control/data signal, and a soundingreference signal (SRS) used for UL channel measurement are defined as ULphysical signals.

In the present disclosure, the PDCCH/PCFICH/PHICH/PDSCH refers to a setof time-frequency resources or a set of REs, which carry downlinkcontrol information (DCI)/a control format indicator (CFI)/a DLacknowledgement/negative acknowledgement (ACK/NACK)/DL data. Further,the PUCCH/PUSCH/PRACH refers to a set of time-frequency resources or aset of REs, which carry UL control information (UCI)/UL data/a randomaccess signal. In the present disclosure, particularly a time-frequencyresource or an RE which is allocated to or belongs to thePDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to as a PDCCHRE/PCFICH RE/PHICH RE/PDSCH RE/PUCCH RE/PUSCH RE/PRACH RE or a PDCCHresource/PCFICH resource/PHICH resource/PDSCH resource/PUCCHresource/PUSCH resource/PRACH resource. Hereinbelow, if it is said thata UE transmits a PUCCH/PUSCH/PRACH, this means that UCI/UL data/a randomaccess signal is transmitted on or through the PUCCH/PUSCH/PRACH.Further, if it is said that a gNB transmits a PDCCH/PCFICH/PHICH/PDSCH,this means that DCI/control information is transmitted on or through thePDCCH/PCFICH/PHICH/PDSCH.

Hereinbelow, an orthogonal frequency division multiplexing (OFDM)symbol/carrier/subcarrier/RE to which a CRS/DMRS/CSI-RS/SRS/UE-RS isallocated to or for which the CRS/DMRS/CSI-RS/SRS/UE-RS is configured isreferred to as a CRS/DMRS/CSI-RS/SRS/UE-RS symbol/carrier/subcarrier/RE.For example, an OFDM symbol to which a tracking RS (TRS) is allocated orfor which the TRS is configured is referred to as a TRS symbol, asubcarrier to which a TRS is allocated or for which the TRS isconfigured is referred to as a TRS subcarrier, and an RE to which a TRSis allocated or for which the TRS is configured is referred to as a TRSRE. Further, a subframe configured to transmit a TRS is referred to as aTRS subframe. Further, a subframe carrying a broadcast signal isreferred to as a broadcast subframe or a PBCH subframe, and a subframecarrying a synchronization signal (SS) (e.g., a primary synchronizationsignal (PSS) and/or a secondary synchronization signal (SSS)) isreferred to as an SS subframe or a PSS/SSS subframe. An OFDMsymbol/subcarrier/RE to which a PSS/SSS is allocated or for which thePSS/SSS is configured is referred to as a PSS/SSS symbol/subcarrier/RE.

In the present disclosure, a CRS port, a UE-RS port, a CSI-RS port, anda TRS port refer to an antenna port configured to transmit a CRS, anantenna port configured to transmit a UE-RS, an antenna port configuredto transmit a CSI-RS, and an antenna port configured to transmit a TRS,respectively. Antenna port configured to transmit CRSs may bedistinguished from each other by the positions of REs occupied by theCRSs according to CRS ports, antenna ports configured to transmit UE-RSsmay be distinguished from each other by the positions of REs occupied bythe UE-RSs according to UE-RS ports, and antenna ports configured totransmit CSI-RSs may be distinguished from each other by the positionsof REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, theterm CRS/UE-RS/CSI-RS/TRS port is also used to refer to a pattern of REsoccupied by a CRS/UE-RS/CSI-RS/TRS in a predetermined resource area.

FIG. 1 illustrates control-plane and user-plane protocol stacks in aradio interface protocol architecture conforming to a 3GPP wirelessaccess network standard between a user equipment (UE) and an evolvedUMTS terrestrial radio access network (E-UTRAN). The control plane is apath in which the UE and the E-UTRAN transmit control messages to managecalls, and the user plane is a path in which data generated from anapplication layer, for example, voice data or Internet packet data istransmitted.

A physical (PHY) layer at layer 1 (L1) provides information transferservice to its higher layer, a medium access control (MAC) layer. ThePHY layer is connected to the MAC layer via transport channels. Thetransport channels deliver data between the MAC layer and the PHY layer.Data is transmitted on physical channels between the PHY layers of atransmitter and a receiver. The physical channels use time and frequencyas radio resources. Specifically, the physical channels are modulated inorthogonal frequency division multiple access (OFDMA) for downlink (DL)and in single carrier frequency division multiple access (SC-FDMA) foruplink (UL).

The MAC layer at layer 2 (L2) provides service to its higher layer, aradio link control (RLC) layer via logical channels. The RLC layer at L2supports reliable data transmission. RLC functionality may beimplemented in a function block of the MAC layer. A packet dataconvergence protocol (PDCP) layer at L2 performs header compression toreduce the amount of unnecessary control information and thusefficiently transmit Internet protocol (IP) packets such as IP version 4(IPv4) or IP version 6 (IPv6) packets via an air interface having anarrow bandwidth.

A radio resource control (RRC) layer at the lowest part of layer 3 (orL3) is defined only on the control plane. The RRC layer controls logicalchannels, transport channels, and physical channels in relation toconfiguration, reconfiguration, and release of radio bearers. A radiobearer refers to a service provided at L2, for data transmission betweenthe UE and the E-UTRAN. For this purpose, the RRC layers of the UE andthe E-UTRAN exchange RRC messages with each other. If an RRC connectionis established between the UE and the E-UTRAN, the UE is in RRCConnected mode and otherwise, the UE is in RRC Idle mode. A Non-AccessStratum (NAS) layer above the RRC layer performs functions includingsession management and mobility management.

DL transport channels used to deliver data from the E-UTRAN to UEsinclude a broadcast channel (BCH) carrying system information, a pagingchannel (PCH) carrying a paging message, and a shared channel (SCH)carrying user traffic or a control message. DL multicast traffic orcontrol messages or DL broadcast traffic or control messages may betransmitted on a DL SCH or a separately defined DL multicast channel(MCH). UL transport channels used to deliver data from a UE to theE-UTRAN include a random access channel (RACH) carrying an initialcontrol message and a UL SCH carrying user traffic or a control message.Logical channels that are defined above transport channels and mapped tothe transport channels include a broadcast control channel (BCCH), apaging control channel (PCCH), a Common Control Channel (CCCH), amulticast control channel (MCCH), a multicast traffic channel (MTCH),etc.

FIG. 2 illustrates physical channels and a general method fortransmitting signals on the physical channels in the 3GPP system.

Referring to FIG. 2, when a UE is powered on or enters a new cell, theUE performs initial cell search (S201). The initial cell search involvesacquisition of synchronization to an eNB. Specifically, the UEsynchronizes its timing to the eNB and acquires a cell identifier (ID)and other information by receiving a primary synchronization channel(P-SCH) and a secondary synchronization channel (S-SCH) from the eNB.Then the UE may acquire information broadcast in the cell by receiving aphysical broadcast channel (PBCH) from the eNB. During the initial cellsearch, the UE may monitor a DL channel state by receiving a DownLinkreference signal (DL RS).

After the initial cell search, the UE may acquire detailed systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation included in the PDCCH (S202).

If the UE initially accesses the eNB or has no radio resources forsignal transmission to the eNB, the UE may perform a random accessprocedure with the eNB (S203 to S206). In the random access procedure,the UE may transmit a predetermined sequence as a preamble on a physicalrandom access channel (PRACH) (S203 and S205) and may receive a responsemessage to the preamble on a PDCCH and a PDSCH associated with the PDCCH(S204 and S206). In the case of a contention-based RACH, the UE mayadditionally perform a contention resolution procedure.

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S207) and transmit a physical uplink shared channel(PUSCH) and/or a physical uplink control channel (PUCCH) to the eNB(S208), which is a general DL and UL signal transmission procedure.Particularly, the UE receives downlink control information (DCI) on aPDCCH. Herein, the DCI includes control information such as resourceallocation information for the UE. Different DCI formats are definedaccording to different usages of DCI.

Control information that the UE transmits to the eNB on the UL orreceives from the eNB on the DL includes a DL/UL acknowledgment/negativeacknowledgment (ACK/NACK) signal, a channel quality indicator (CQI), aprecoding matrix index (PMI), a rank indicator (RI), etc. In the 3GPPLTE system, the UE may transmit control information such as a CQI, aPMI, an RI, etc. on a PUSCH and/or a PUCCH.

FIG. 3 is a diagram illustrating a radio frame structure fortransmitting a synchronization signal (SS) in LTE system. In particular,FIG. 3 illustrates a radio frame structure for transmitting asynchronization signal and PBCH in frequency division duplex (FDD). FIG.3(a) shows positions at which the SS and the PBCH are transmitted in aradio frame configured by a normal cyclic prefix (CP) and FIG. 3(b)shows positions at which the SS and the PBCH are transmitted in a radioframe configured by an extended CP.

An SS will be described in more detail with reference to FIG. 3. An SSis categorized into a primary synchronization signal (PSS) and ansecondary synchronization signal (SSS). The PSS is used to acquiretime-domain synchronization such as OFDM symbol synchronization, slotsynchronization, etc. and/or frequency-domain synchronization. And, theSSS is used to acquire frame synchronization, a cell group ID, and/or aCP configuration of a cell (i.e. information indicating whether to anormal CP or an extended is used). Referring to FIG. 4, a PSS and an SSSare transmitted through two OFDM symbols in each radio frame.Particularly, the SS is transmitted in first slot in each of subframe 0and subframe 5 in consideration of a GSM (Global System for Mobilecommunication) frame length of 4.6 ms for facilitation of inter-radioaccess technology (inter-RAT) measurement. Especially, the PSS istransmitted in a last OFDM symbol in each of the first slot of subframe0 and the first slot of subframe 5. And, the SSS is transmitted in asecond to last OFDM symbol in each of the first slot of subframe 0 andthe first slot of subframe 5. Boundaries of a corresponding radio framemay be detected through the SSS. The PSS is transmitted in the last OFDMsymbol of the corresponding slot and the SSS is transmitted in the OFDMsymbol immediately before the OFDM symbol in which the PSS istransmitted. According to a transmission diversity scheme for the SS,only a single antenna port is used. However, the transmission diversityscheme for the SS standards is not separately defined in the currentstandard.

Referring to FIG. 3, by detecting the PSS, a UE may know that acorresponding subframe is one of subframe 0 and subframe 5 since the PSSis transmitted every 5 ms but the UE cannot know whether the subframe issubframe 0 or subframe 5. That is, frame synchronization cannot beobtained only from the PSS. The UE detects the boundaries of the radioframe in a manner of detecting an SSS which is transmitted twice in oneradio frame with different sequences.

Having demodulated a DL signal by performing a cell search procedureusing the PSS/SSS and determined time and frequency parameters necessaryto perform UL signal transmission at an accurate time, a UE cancommunicate with an eNB only after obtaining system informationnecessary for a system configuration of the UE from the eNB.

The system information is configured with a master information block(MIB) and system information blocks (SIBs). Each SIB includes a set offunctionally related parameters and is categorized into an MIB, SIB Type1 (SIB1), SIB Type 2 (SIB2), and SIB3 to SIB8 according to the includedparameters.

The MIB includes most frequently transmitted parameters which areessential for a UE to initially access a network served by an eNB. TheUE may receive the MIB through a broadcast channel (e.g. a PBCH). TheMIB includes a downlink system bandwidth (DL BW), a PHICH configuration,and a system frame number (SFN). Thus, the UE can explicitly knowinformation on the DL BW, SFN, and PHICH configuration by receiving thePBCH. On the other hand, the UE may implicitly know information on thenumber of transmission antenna ports of the eNB. The information on thenumber of the transmission antennas of the eNB is implicitly signaled bymasking (e.g. XOR operation) a sequence corresponding to the number ofthe transmission antennas to 16-bit cyclic redundancy check (CRC) usedin detecting an error of the PBCH.

The SIB1 includes not only information on time-domain scheduling forother SIBs but also parameters necessary to determine whether a specificcell is suitable in cell selection. The UE receives the SIB1 viabroadcast signaling or dedicated signaling.

A DL carrier frequency and a corresponding system bandwidth can beobtained by MIB carried by PBCH. A UL carrier frequency and acorresponding system bandwidth can be obtained through systeminformation corresponding to a DL signal. Having received the MIB, ifthere is no valid system information stored in a corresponding cell, aUE applies a value of a DL BW included in the MIB to a UL bandwidthuntil system information block type 2 (SystemInformationBlockType2,SIB2) is received. For example, if the UE obtains the SIB2, the UE isable to identify the entire UL system bandwidth capable of being usedfor UL transmission through UL-carrier frequency and UL-bandwidthinformation included in the SIB2.

In the frequency domain, PSS/SSS and PBCH are transmitted irrespectiveof an actual system bandwidth in total 6 RBs, i.e., 3 RBs in the leftside and 3 RBs in the right side with reference to a DC subcarrierwithin a corresponding OFDM symbol. In other words, the PSS/SSS and thePBCH are transmitted only in 72 subcarriers. Therefore, a UE isconfigured to detect or decode the SS and the PBCH irrespective of adownlink transmission bandwidth configured for the UE.

Having completed the initial cell search, the UE can perform a randomaccess procedure to complete the accessing the eNB. To this end, the UEtransmits a preamble via PRACH (physical random access channel) and canreceive a response message via PDCCH and PDSCH in response to thepreamble. In case of contention based random access, it may transmitadditional PRACH and perform a contention resolution procedure such asPDCCH and PDSCH corresponding to the PDCCH.

Having performed the abovementioned procedure, the UE can performPDCCH/PDSCH reception and PUSCH/PUCCH transmission as a general UL/DLsignal transmission procedure.

The random access procedure is also referred to as a random accesschannel (RACH) procedure. The random access procedure is used forvarious usages including initial access, UL synchronization adjustment,resource allocation, handover, and the like. The random access procedureis categorized into a contention-based procedure and a dedicated (i.e.,non-contention-based) procedure. In general, the contention-based randomaccess procedure is used for performing initial access. On the otherhand, the dedicated random access procedure is restrictively used forperforming handover, and the like. When the contention-based randomaccess procedure is performed, a UE randomly selects a RACH preamblesequence. Hence, a plurality of UEs can transmit the same RACH preamblesequence at the same time. As a result, a contention resolutionprocedure is required thereafter. On the contrary, when the dedicatedrandom access procedure is performed, the UE uses an RACH preamblesequence dedicatedly allocated to the UE by an eNB. Hence, the UE canperform the random access procedure without a collision with a differentUE.

The contention-based random access procedure includes 4 steps describedin the following. Messages transmitted via the 4 steps can berespectively referred to as message (Msg) 1 to 4 in the presentinvention.

-   -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response (RAR) (via PDCCH and PDSCH (eNB        to)    -   Step 3: Layer 2/Layer 3 message (via PUSCH) (UE to eNB)    -   Step 4: Contention resolution message (eNB to UE)

On the other hand, the dedicated random access procedure includes 3steps described in the following. Messages transmitted via the 3 stepscan be respectively referred to as message (Msg) 0 to 2 in the presentinvention. It may also perform uplink transmission (i.e., step 3)corresponding to PAR as a part of the ransom access procedure. Thededicated random access procedure can be triggered using PDCCH(hereinafter, PDCCH order) which is used for an eNB to indicatetransmission of an RACH preamble.

-   -   Step 0: RACH preamble assignment via dedicated signaling (eNB to        UE)    -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response (RAR) (via PDCCH and PDSCH) (eNB        to UE)

After the RACH preamble is transmitted, the UE attempts to receive arandom access response (RAR) in a preconfigured time window.Specifically, the UE attempts to detect PDCCH (hereinafter, RA-RNTIPDCCH) (e.g., a CRC masked with RA-RNTI in PDCCH) having RA-RNTI (randomaccess RNTI) in a time window. If the RA-RNTI PDCCH is detected, the UEchecks whether or not there is a RAR for the UE in PDSCH correspondingto the RA-RNTI PDCCH. The RAR includes timing advance (TA) informationindicating timing offset information for UL synchronization, UL resourceallocation information (UL grant information), a temporary UE identifier(e.g., temporary cell-RNTI, TC-RNTI), and the like. The UE can performUL transmission (e.g., message 3) according to the resource allocationinformation and the TA value included in the RAR. HARQ is applied to ULtransmission corresponding to the RAR. In particular, the UE can receivereception response information (e.g., PHICH) corresponding to themessage 3 after the message 3 is transmitted.

A random access preamble (i.e. RACH preamble) consists of a cyclicprefix of a length of TCP and a sequence part of a length of TSEQ. TheTCP and the TSEQ depend on a frame structure and a random accessconfiguration. A preamble format is controlled by higher layer. The RACHpreamble is transmitted in a UL subframe. Transmission of the randomaccess preamble is restricted to a specific time resource and afrequency resource. The resources are referred to as PRACH resources. Inorder to match an index 0 with a PRB and a subframe of a lower number ina radio frame, the PRACH resources are numbered in an ascending order ofPRBs in subframe numbers in the radio frame and frequency domain. Randomaccess resources are defined according to a PRACH configuration index(refer to 3GPP TS 36.211 standard document). The RACH configurationindex is provided by a higher layer signal (transmitted by an eNB).

In the LTE/LTE-A system, a subcarrier spacing for a random accesspreamble (i.e., RACH preamble) is regulated by 1.25 kHz and 7.5 kHz forpreamble formats 0 to 3 and a preamble format 4, respectively (refer to3GPP TS 36.211).

<OFDM Numerology>

A New RAT system adopts an OFDM transmission scheme or a transmissionscheme similar to the OFDM transmission scheme. The New RAT system mayuse different OFDM parameters from LTE OFDM parameters. Or the New RATsystem may follow the numerology of legacy LTE/LTE-A but have a largersystem bandwidth (e.g., 100 MHz). Or one cell may support a plurality ofnumerologies. That is, UEs operating with different numerologies mayco-exist within one cell.

<Subframe Structure>

In the 3GPP LTE/LTE-A system, a radio frame is 10 ms(307200 T_(s)) long,including 10 equal-size subframes (SFs). The 10 SFs of one radio framemay be assigned numbers. T_(s) represents a sampling time and isexpressed as T_(s)=1/(2048*15 kHz). Each SF is 1 ms, including twoslots. The 20 slots of one radio frame may be sequentially numbered from0 to 19. Each slot has a length of 0.5 ms. A time taken to transmit oneSF is defined as a transmission time interval (TTI). A time resource maybe distinguished by a radio frame number (or radio frame index), an SFnumber (or SF index), a slot number (or slot index), and so on. A TTIrefers to an interval in which data may be scheduled. In the currentLTE/LTE-A system, for example, there is a UL grant or DL granttransmission opportunity every 1 ms, without a plurality of UL/DL grantopportunities for a shorter time than 1 ms. Accordingly, a TTI is 1 msin the legacy LTE/LTE-A system.

FIG. 4 illustrates an exemplary slot structure available in the newradio access technology (NR).

To minimize a data transmission delay, a slot structure in which acontrol channel and a data channel are multiplexed in time divisionmultiplexing (TDM) is considered in 5^(th) generation (5G) NR.

In FIG. 4, an area marked with slanted lines represents a transmissionregion of a DL control channel (e.g., PDCCH) carrying DCI, and a blackpart represents a transmission region of a UL control channel (e.g.,PUCCH) carrying UCI. DCI is control information that a gNB transmits toa UE, and may include information about a cell configuration that a UEshould know, DL-specific information such as DL scheduling, andUL-specific information such as a UL grant. Further, UCI is controlinformation that a UE transmits to a gNB. The UCI may include an HARQACK/NACK report for DL data, a CSI report for a DL channel state, ascheduling request (SR), and so on.

In FIG. 4, symbols with symbol index 1 to symbol index 12 may be usedfor transmission of a physical channel (e.g., PDSCH) carrying DL data,and also for transmission of a physical channel (e.g., PUSCH) carryingUL data. According to the slot structure illustrated in FIG. 2, as DLtransmission and UL transmission take place sequentially in one slot,transmission/reception of DL data and reception/transmission of a ULACK/NACK for the DL data may be performed in the one slot. As aconsequence, when an error is generated during data transmission, a timetaken for a data retransmission may be reduced, thereby minimizing thedelay of a final data transmission.

In this slot structure, a time gap is required to allow a gNB and a UEto switch from a transmission mode to a reception mode or from thereception mode to the transmission mode. For the switching between thetransmission mode and the reception mode, some OFDM symbol correspondingto a DL-to-UL switching time is configured as a guard period (GP) in theslot structure.

In the legacy LTE/LTE-A system, a DL control channel is multiplexed witha data channel in TDM, and a control channel, PDCCH is transmitteddistributed across a total system band. In NR, however, it is expectedthat the bandwidth of one system will be at least about 100 MHz, whichmakes it inviable to transmit a control channel across a total band. Ifa UE monitors the total band to receive a DL control channel, for datatransmission/reception, this may increase the battery consumption of theUE and decrease efficiency. Therefore, a DL control channel may betransmitted localized or distributed in some frequency band within asystem band, that is, a channel band in the present disclosure.

In the NR system, a basic transmission unit is a slot. A slot durationincludes 14 symbols each having a normal cyclic prefix (CP), or 12symbols each having an extended CP. Further, a slot is scaled in time bya function of a used subcarrier spacing. That is, as the subcarrierspacing increases, the length of a slot decreases. For example, given 14symbols per slot, if the number of slots in a 10-ms frame is 10 for asubcarrier spacing of 15 kHz, the number of slots is 20 for a subcarrierspacing of 30 kHz, and 40 for a subcarrier spacing of 60 kHz. As thesubcarrier spacing increases, the length of an OFDM symbol decreases.The number of OFDM symbols per slot is different depending on the normalCP or the extended CP, and does not change according to a subcarrierspacing. The basic time unit for LTE, T_(s) is defined as 1/(15000*2048)seconds, in consideration of the basic 15-kHz subcarrier spacing and amaximum FFT size of 2048. T_(s) is also a sampling time for the 15-kHzsubcarrier spacing. In the NR system, many other subcarrier spacingsthan 15 kHz are available, and since a subcarrier spacing is inverselyproportional to a corresponding time length, an actual sampling timeT_(s) corresponding to subcarrier spacings larger than 15 kHz becomesshorter than 1/(15000*2048) seconds. For example, the actual samplingtime for the subcarrier spacings of 30 kHz, 60 kHz, and 120 kHz may be1/(2*15000*2048) seconds, 1/(4*15000*2048) seconds, and 1/(8*15000*2048)seconds, respectively.

<Analog Beamforming>

For a 5G mobile communication system under discussion, a technique ofusing an ultra-high frequency band, that is, a millimeter frequency bandat or above 6 GHz is considered in order to transmit data to a pluralityof users at a high transmission rate in a wide frequency band. The 3GPPcalls this technique NR, and thus a 5G mobile communication system willbe referred to as an NR system in the present disclosure. However, themillimeter frequency band has the frequency property that a signal isattenuated too rapidly according to a distance due to the use of toohigh a frequency band. Accordingly, the NR system using a frequency bandat or above at least 6 GHz employs a narrow beam transmission scheme inwhich a signal is transmitted with concentrated energy in a specificdirection, not omni-directionally, to thereby compensate for the rapidpropagation attenuation and thus overcome the decrease of coveragecaused by the rapid propagation attenuation. However, if a service isprovided by using only one narrow beam, the service coverage of one gNBbecomes narrow, and thus the gNB provides a service in a wideband bycollecting a plurality of narrow beams.

As a wavelength becomes short in the millimeter frequency band, that is,millimeter wave (mmW) band, it is possible to install a plurality ofantenna elements in the same area. For example, a total of 100 antennaelements may be installed at (wavelength) intervals of 0.5 lamda in a30-GHz band with a wavelength of about 1 cm in a two-dimensional (2D)array on a 5 by 5 cm panel. Therefore, it is considered to increasecoverage or throughput by increasing a beamforming gain through use of aplurality of antenna elements in mmW.

To form a narrow beam in the millimeter frequency band, a beamformingscheme is mainly considered, in which a gNB or a UE transmits the samesignals with appropriate phase differences through multiple antennas, tothereby increase energy only in a specific direction. Such beamformingschemes include digital beamforming for generating a phase differencebetween digital baseband signals, analog beamforming for generating aphase difference between modulated analog signals by using a time delay(i.e., a cyclic shift), and hybrid beamforming using both digitalbeamforming and analog beamforming. If a TXRU is provided per antennaelement to enable control of transmission power and a phase per antenna,independent beamforming per frequency resource is possible. However,installation of TXRUs for all of about 100 antenna elements is noteffective in terms of cost. That is, to compensate for rapid propagationattenuation in the millimeter frequency band, multiple antennas shouldbe used, and digital beamforming requires as many RF components (e.g.,digital to analog converters (DACs), mixers, power amplifiers, andlinear amplifiers) as the number of antennas. Accordingly,implementation of digital beamforming in the millimeter frequency bandfaces the problem of increased cost of communication devices. Therefore,in the case where a large number of antennas are required as in themillimeter frequency band, analog beamforming or hybrid beamforming isconsidered. In analog beamforming, a plurality of antenna elements aremapped to one TXRU, and the direction of a beam is controlled by ananalog phase shifter. A shortcoming with this analog beamforming schemeis that frequency selective beamforming (BF) cannot be provided becauseonly one beam direction can be produced in a total band. Hybrid BFstands between digital BF and analog BF, in which B TXRUs fewer than Qantenna elements are used. In hybrid BF, the directions of beamstransmittable at the same time is limited to or below B although thenumber of beam directions is different according to connections betweenB TXRUs and Q antenna elements.

FIG. 5 is a view illustrating exemplary connection schemes between TXRUsand antenna elements.

(a) of FIG. 5 illustrates connection between a TXRU and a sub-array. Inthis case, an antenna element is connected only to one TXRU. Incontrast, (b) of FIG. 5 illustrates connection between a TXRU and allantenna elements. In this case, an antenna element is connected to allTXRUs. In FIG. 5, W represents a phase vector subjected tomultiplication in an analog phase shifter. That is, a direction ofanalog beamforming is determined by W. Herein, CSI-RS antenna ports maybe mapped to TXRUs in a one-to-one or one-to-many correspondence.

As mentioned before, since a digital baseband signal to be transmittedor a received digital baseband signal is subjected to a signal processin digital beamforming, a signal may be transmitted or received in orfrom a plurality of directions on multiple beams. In contrast, in analogbeamforming, an analog signal to be transmitted or a received analogsignal is subjected to beamforming in a modulated state. Thus, signalscannot be transmitted or received simultaneously in or from a pluralityof directions beyond the coverage of one beam. A gNB generallycommunicates with multiple users at the same time, relying on thewideband transmission or multiple antenna property. If the gNB usesanalog BF or hybrid BF and forms an analog beam in one beam direction,the gNB has no way other than to communicate only with users covered inthe same analog beam direction in view of the nature of analog BF. Alater-described RACH resource allocation and gNB resource utilizationscheme according to the present invention is proposed by reflectinglimitations caused by the nature of analog BF or hybrid BF.

<Hybrid Analog Beamforming>

FIG. 6 abstractly illustrates a hybrid beamforming structure in terms ofTXRUs and physical antennas.

For the case where multiple antennas are used, hybrid BF with digital BFand analog BF in combination has emerged. Analog BF (or RF BF) is anoperation of performing precoding (or combining) in an RF unit. Due toprecoding (combining) in each of a baseband unit and an RF unit, hybridBF offers the benefit of performance close to the performance of digitalBF, while reducing the number of RF chains and the number of DACs (oranalog to digital converters (ADCs). For the convenience' sake, a hybridBF structure may be represented by N TXRUs and M physical antennas.Digital BF for L data layers to be transmitted by a transmission end maybe represented as an N-by-N matrix, and then N converted digital signalsare converted to analog signals through TXRUs and subjected to analog BFrepresented as an M-by-N matrix. In FIG. 6, the number of digital beamsis L, and the number of analog beams is N. Further, it is considered inthe NR system that a gNB is configured to change analog BF on a symbolbasis so as to more efficiently support BF for a UE located in aspecific area. Further, when one antenna panel is defined by N TXRUs andM RF antennas, introduction of a plurality of antenna panels to whichindependent hybrid BF is applicable is also considered. As such, in thecase where a gNB uses a plurality of analog beams, a different analogbeam may be preferred for signal reception at each UE. Therefore, a beamsweeping operation is under consideration, in which for at least an SS,system information, and paging, a gNB changes a plurality of analogbeams on a symbol basis in a specific slot or SF to allow all UEs tohave reception opportunities.

FIG. 7 is a view illustrating beam sweeping for an SS and systeminformation during DL transmission. In FIG. 7, physical resources or aphysical channel which broadcasts system information of the New RATsystem is referred to as an xPBCH. Analog beams from different antennapanels may be transmitted simultaneously in one symbol, and introductionof a beam reference signal (BRS) transmitted for a single analog beamcorresponding to a specific antenna panel as illustrated in FIG. 7 isunder discussion in order to measure a channel per analog beam. BRSs maybe defined for a plurality of antenna ports, and each antenna port ofthe BRSs may correspond to a single analog beam. Unlike the BRSs, the SSor the xPBCH may be transmitted for all analog beams included in ananalog beam group so that any UE may receive the SS or the xPBCHsuccessfully.

FIG. 8 is a view illustrating an exemplary cell in the NR system.

Referring to FIG. 8, compared to a wireless communication system such aslegacy LTE in which one eNB forms one cell, configuration of one cell bya plurality of TRPs is under discussion in the NR system. If a pluralityof TRPs form one cell, even though a TRP serving a UE is changed,seamless communication is advantageously possible, thereby facilitatingmobility management for UEs.

Compared to the LTE/LTE-A system in which a PSS/SSS is transmittedomni-directionally, a method for transmitting a signal such as aPSS/SSS/PBCH through BF performed by sequentially switching a beamdirection to all directions at a gNB applying mmWave is considered. Thesignal transmission/reception performed by switching a beam direction isreferred to as beam sweeping or beam scanning. In the presentdisclosure, “beam sweeping” is a behavior of a transmission side, and“beam scanning” is a behavior of a reception side. For example, if up toN beam directions are available to the gNB, the gNB transmits a signalsuch as a PSS/SSS/PBCH in the N beam directions. That is, the gNBtransmits an SS such as the PSS/SSS/PBCH in each direction by sweeping abeam in directions available to or supported by the gNB. Or if the gNBis capable of forming N beams, the beams may be grouped, and thePSS/SSS/PBCH may be transmitted/received on a group basis. One beamgroup includes one or more beams. Signals such as the PSS/SSS/PBCHtransmitted in the same direction may be defined as one SS block (SSB),and a plurality of SSBs may exist in one cell. If a plurality of SSBsexist, an SSB index may be used to identify each SSB. For example, ifthe PSS/SSS/PBCH is transmitted in 10 beam directions in one system, thePSS/SSS/PBCH transmitted in the same direction may form an SSB, and itmay be understood that 10 SSBs exist in the system. In the presentdisclosure, a beam index may be interpreted as an SSB index.

Now, a description will be given of a method for indicating the timeindex of a time at which an SS is transmitted, and a method forconfiguring a DL bandwidth by an SS according to an embodiment of thepresent disclosure.

1. SS Block Configuration

If the maximum size of payload of the PBCH is 80 bits, a total of fourOFDM symbols may be used for transmission of an SS block. Meanwhile,there is a need for discussing the time positions of an NR-PSS, anNR-SSS, and an NR-PBCH included in an SSB. In an initial access state,the NR-PBCH may be used as a reference signal for accuratetime/frequency tracking. To increase tracking accuracy, it is efficientto separate two OFDM symbols for the NR-PBCH as far as possible.Therefore, the first and fourth OFDM symbols of the SSB may be used fortransmission of the NR-PBCH. Accordingly, the second OFDM symbol may beallocated to the NR-PSS, and the third OFDM symbol may be used for theNR-SSS.

The results of measuring PBCH decoding performance according to thenumber of REs for DMRSs reveal that if two OFDM symbols are allocated tothe PBCH, 192 REs may be used for DMRSs, and 384 REs may be used fordata. In this case, on the assumption that the PBCH payload size is 64bits, a 1/12 coding speed equal to that of an LTE PBCH may be achieved.

A method for mapping encoded NR-PBCH bits to REs in a PBCH symbol may beconsidered. However, this method has a shortcoming in interference anddecoding performance. On the other hand, if the encoded NR-PBCH bits aremapped across REs included in N PBCH symbols, this method may havebetter performance in interference and decoding performance.

Meanwhile, a comparison between bits encoded in the same method in twoOFDM symbols and bits encoded in different methods in two OFDM symbolsreveals that the latter offers better performance because the encodedbits have more redundant bits. Accordingly, it may be considered to usebits encoded in different methods in two OFDM symbols.

In addition, a plurality of numerologies are supported in the NR system.Therefore, a numerology for SSB transmission may be different from anumerology for data transmission. Further, if different types ofchannels such as the PBCH and the PDSCH are multiplexed in the frequencydomain, spectral emission may bring about inter-carrier interference(ICI) and thus performance degradation. To solve the problem, a guardfrequency may be introduced between the PBCH and the PDSCH. Further, toreduce the effect of ICI, a network may allocate data RBs such that thedata RBs are not adjacent to each other.

However, the foregoing method is not efficient in that a large number ofREs should be reserved as a guard frequency. Thus, it may be moreefficient to reserve one or more subcarriers at an edge as a guardfrequency within a PBCH transmission bandwidth. The accurate number ofreserved REs may be changed according to the subcarrier spacing of thePBCH. For example, for the 15-kHz subcarrier spacing for PBCHtransmission, two subcarriers may be reserved at each edge of the PBCHtransmission bandwidth. On the other hand, for the 30-kHz subcarrierspacing for PBCH transmission, one subcarrier may be reserved.

Referring to FIG. 9(a), the NR-PBCH is allocated within 288 REs whichform 24 RBs. Meanwhile, since the sequence of the NR-PSS/NR-SSS is oflength 127, 12 RBs are required to transmit the NR-PSS/NR-SSS. That is,when an SSB is configured, the SSB is allocated in 24 RBs. Further, itis also preferred to allocate the SSB in 24 RBs for RB grid alignmentbetween different numerologies such as 15, 30, and 60 kHz. Further,since a minimum bandwidth of 5 MHz in which 25 RBs can be defined withthe 15-kHz subcarrier spacing is assumed in NR, 24 RBs are used for SSBtransmission. In addition, the NR-PSS/SSS should be positioned in themiddle of the SSB, which may imply that the NR-PSS/SSS is allocated in7^(th) to 18^(th) RBs.

Meanwhile, if an SSB is configured as illustrated in FIG. 9(a), aproblem may occur to an automatic gain control (AGC) operation of a UEat subcarrier spacings of 120 kHz and 240 kHz. That is, for thesubcarrier spacings of 120 kHz and 240 kHz, the NR-PSS may not bedetected successfully due to the AGC operation. In this context, it maybe considered to change the SSB configuration in the following twoembodiments.

(Method 1) PBCH-PSS-PBCH-SSS

(Method 2) PBCH-PSS-PBCH-SSS-PBCH

That is, PBCH symbols may be positioned at the start of the SSB, andused as dummy symbols for the AGC operation, so that the UE performs theAGC operation more reliably.

Meanwhile, the NR-PSS/NR-SSS/NR-PBCH may be allocated as illustrated inFIG. 9(b). that is, the NR-PSS may be allocated to symbol 0, and theNR-SSS may be allocated to symbol 2. The NR-PBCH may be allocated tosymbol 1 to symbol 3. Herein, symbol 1 and symbol 3 may be dedicated tothe NR-PBCH. In other words, only the NR-PBCH may be mapped to symbol 1and symbol 3, and the NR-SSS and the NR-PBCH may be mapped together tosymbol 2.

2. SS Burst Set Configuration

FIG. 10 illustrates SS burst sets configured at a subcarrier spacing of120 kHz and a subcarrier spacing of 240 kHz, respectively. Referring toFIG. 10, for the subcarrier spacings of 120 kHz and 240 kHz, SS burstsare configured with a predetermined gap every four SS bursts. That is,SSBs are arranged with a 0.125-ms symbol period for UL transmissionemptied every 0.5 ms.

However, a subcarrier spacing of 60 kHz may be used for datatransmission in a frequency band at or above 6 GHz. That is, asillustrated in FIG. 11, the 60-kHz subcarrier spacing for datatransmission and the 120-kHz subcarrier spacing or 240 kHz for SSBtransmission may be multiplexed in NR.

Meanwhile, it can be seen from a part marked with a square in FIG. 11that as an SSB with the 120-kHz subcarrier spacing is multiplexed withdata with the 60-kHz subcarrier spacing, the SSB with the 120-kHzsubcarrier spacing, and a GP and a DL control region with the 60-kHzsubcarrier spacing collide or overlap with each other. Since thecollision between the SSB and the DL/UL control region should preferablybe avoided, the configurations of an SS burst and an SS burst set needto be modified.

In the present disclosure, two embodiments are proposed to modify the SSburst configuration in order to avert the above problem.

One of the embodiments is to change the positions of SS burst format 1and SS burst format 2 as illustrated in FIG. 12. That is, SS burstformat 1 and SS burst format 2 in the square box illustrated in FIG. 11are exchanged as illustrated in FIG. 12, to prevent collision betweenthe SSB and the DL/UL control region. In other words, SS burst format 1is positioned at the start of a slot with the 60-kHz subcarrier spacing,and SS burst format 2 is positioned at the end of the slot with the60-kHz subcarrier spacing.

The above embodiment may be summarized as follows.

1) 120-kHz Subcarrier Spacing

-   -   The first OFDM symbols of candidate SSBs have indexes {4, 8, 16,        20, 32, 36, 44, 48}+70*n. For carrier frequencies larger than 6        GHz, n=0, 2, 4, 6.    -   The first OFDM symbols of candidate SSBs have indexes {2, 6, 18,        22, 30, 34, 46, 50}+70*n. For carrier frequencies larger than 6        GHz, n=1, 3, 5, 7.

2) 240-kHz Subcarrier Spacing

-   -   The first OFDM symbols of candidate SSBs have indexes {8, 12,        16, 20, 32, 36, 40, 44, 64, 68, 72, 76, 88, 92, 96, 100}+140*n.        For carrier frequencies larger than 6 GHz, n=0, 2.    -   The first OFDM symbols of candidate SSBs have indexes {4, 8, 12,        16, 36, 40, 44, 48, 60, 64, 68, 72, 92, 96, 100, 104}+140*n. For        carrier frequencies larger than 6 GHz, n=1, 3.

The other embodiment is to change the SS burst set configuration, asillustrated in FIG. 13. That is, the SS burst set may be configured suchthat the start boundary of the SS burst set is aligned with, that is,matches the start boundary of a slot with the 60-kHz subcarrier spacing.

Specifically, an SS burst is configured with SSBs localized for 1 ms.Therefore, an SS burst with the 120-kHz subcarrier spacing has 16 SSBsfor 1 ms, and an SS burst with the 240-kHz subcarrier spacing has 32SSBs for 1 ms. If an SS burst is configured in this manner, one slot isallocated as a gap between SS bursts, with respect to the 60-kHzsubcarrier spacing.

The second embodiment is summarized as follows.

1) 120-kHz Subcarrier Spacing

-   -   The first OFDM symbols of candidate SSBs have indexes {4, 8, 16,        20}+28*n. For carrier frequencies larger than 6 GHz, n=0, 1, 2,        3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18.

2) 240-kHz Subcarrier Spacing

-   -   The first OFDM symbols of candidate SSBs have indexes {8, 12,        16, 20, 32, 36, 40, 44}+56*n. For carrier frequencies larger        than 6 GHz, n=0, 1, 2, 3, 5, 6, 7, 8.

3. Method for Indicating Actual Transmitted SS/PBCH Block Within 5-msPeriod

Meanwhile, the number of candidates for SSB transmission may be limitedaccording to a network environment. For example, the number ofcandidates may be different according to a subcarrier spacing at whichan SSB is arranged. In this case, the position of an actual transmittedSSB may be indicated to a CONNECTED/IDLE-mode UE. Herein, an actualtransmitted SS/PBCH block indication indicating the position of anactual transmitted SSB may be used for the purpose of resourceutilization, for example, rate matching for a serving cell, and for thepurpose of measurement of corresponding resources, for a neighbor cell.

Regarding the serving cell, if a UE can accurately determine anon-transmitted SSB, the UE may determine that other information such aspaging or data may be received in candidate resources of thenon-transmitted SSB. For this resource flexibility, an SSB actuallytransmitted in the serving cell needs to be accurately indicted.

That is, since other information such as paging or data may not bereceived in resources carrying an SSB, the UE needs to know an SSBcandidate which is not actually transmitted in order to increase theefficiency of resource utilization by receiving other data or signals inthe non-transmitted SSB.

Thus, a 4-, 8- or 64-bit full bitmap is required to accurately indicatean SSB that is actually transmitted in a serving cell. The number ofbits included in the bitmap may be determined according to the maximumnumber of SSBs transmittable in each frequency range. For example, inorder to indicate an SSB actually transmitted in a 5-ms period, 8 bitsare required in a frequency range of 3 GHz to 6 GHz, and 64 bits arerequired in a frequency range at or above 6 GHz.

Bits used to indicate an SSB actually transmitted in a serving cell maybe defined by remaining minimum system information (RMSI) or othersystem information (OSI), and the RMSI/OSI includes configurationinformation for data or paging. The actual transmitted SS/PBCH blockindication is associated with a DL resource configuration, and thus itmay be concluded that the RMSI/OSI includes information about an actualtransmitted SSB.

Meanwhile, an actual transmitted SS/PBCH block indication of a neighborcell may be required to measure the neighbor cell. That is, for theneighbor cell measurement, time synchronization information about theneighbor cell needs to be acquired. In the case where the NR system isdesigned such that asynchronous transmission between TRPs is allowed,even though time synchronization information about a neighbor cell isknown, the accuracy of the information may vary with a situation.Accordingly, when time information about a neighbor cell is indicated,the unit of the time information needs to be determined as informationvalid to a UE, while asynchronous transmission between TRPs is assumed.

However, if too many cells are listed, the full bitmap-type indicator islikely to increase signaling overhead too much. Therefore, an indicatorcompressed in various manners may be considered to decrease signalingoverhead. Meanwhile, an indicator for an SSB transmitted in a servingcell may also be compressed in order to reduce signaling overhead aswell as measure a neighbor cell. In other words, the following SS blockindicator may be used to indicate actual transmitted SSBs in theneighbor cell and the serving cell. Further, according to the abovedescription, although an SS burst may be a set of SSBs included in oneslot on each subcarrier, an SS burst may mean an SSB group including apredetermined number of SSBs irrespective of slots, only in thefollowing embodiments.

Referring to FIG. 14, in one of the embodiments, if an SS burst includes8 SSBs, a total of 8 SS bursts may exist in a band at or above 6 GHz inwhich 64 SSBs are available.

SSBs are grouped into SS bursts in order to compress a 64-bit bitmap.Instead of the 64-bit bitmap, 8-bit information may be used to indicatean SS burst including an actual transmitted SSB. If the 8-bit bitmapindicates SS burst #0, SS burst #0 may include one or more actualtransmitted SSBs.

Herein, additional information may be considered to additionallyindicate the number of SSBs transmitted per SS burst. As many SSBs asindicated by the additional information may exist locally in each SSburst.

Therefore, a UE may estimate an actual transmitted SSB by consideringthe number of actual transmitted SSBs per SS burst, indicated by theadditional information, and the bitmap indicating an SS burst includingthe actual transmitted SSBs in combination.

For example, indications in the following Table 1 may be assumed.

TABLE 1 The number of actually 8 bit bitmap transmitted SS/PBCH block(SS/PBCH burst unit) per SS/PBCH burst unit Full bitmap 1 1 0 0 0 0 0 14 (11110000) (11110000) (00000000) (00000000) (00000000) (00000000)(00000000) (11110000)

That is, according to [Table 1], it may be determined from the 8-bitbitmap that SSBs are included in SS burst #0, SS burst #1, and SS burst#7, and it may be determined from the additional information that fourSSBs are included in each SS burst. Therefore, it may be estimated thatSSBs are transmitted at four candidate positions before SS burst #0, SSburst #1, and SS burst #7.

Meanwhile, unlike the above example, the additional information may alsobe transmitted in the form of a bitmap, thereby achieving flexibility inSSB transmission positions.

For example, information related to SS burst transmission may beindicated by a bitmap, and an SSB transmitted in an SS burst may beindicated by other bits.

That is, the total of 64 SSBs are divided into 8 SS bursts (i.e., SSBgroups), and a used SS burst may be indicated to the UE by an 8-bitbitmap. If an SS burst is defined as illustrated in FIG. 14, if the SSburst is multiplexed with a slot with the 60-kHz subcarrier spacing, theSS burst is advantageously aligned with the boundary of a slot with the60-kHz subcarrier spacing. Therefore, if it is indicated by the bitmapwhether an SS burst is used, the UE may determine whether an SSB istransmitted or not, on a slot basis for every subcarrier spacing in afrequency band at or above 6 GHz.

The difference from the foregoing example lies in that the additionalinformation is indicated in the form of a bitmap. In this case, sincebitmap information should be transmitted for 8 SSBs included in each SSburst, 8 bits are needed, and the corresponding additional informationapplies commonly to all SS bursts. For example, if it is indicated bybitmap information for SS bursts that SS burst #0 and SS burst #1 areused, and it is indicated by additional bitmap information for SSBs thatthe first and fifth SSBs are transmitted in an SSB, the first and fifthSSBs in both of SS burst #0 and SS burst #1 are transmitted, and thusthe total number of actual transmitted SSBs is 4.

Meanwhile, some neighbor cells may not be included in a cell list. Theneighbor cells that are not included in the cell list use a defaultformat for actual transmitted SSBs. Due to the use of the defaultformat, the UE may measure the neighbor cells which are not included inthe list. The default format may be predefined or configured by thenetwork.

Meanwhile, if actual transmitted SSB information transmitted in theserving cell does not match actual transmitted SSB informationtransmitted in the neighbor cell, the UE may acquire the actualtransmitted SSB information by giving priority to the actual transmittedSSB information transmitted in the serving cell.

That is, if actual transmitted SSB information is received in the formof a full bitmap and in the form of grouping, the information in theform of the full bitmap is likely to be more accurate, and thus theinformation of the full bitmap may be used with priority in SSBreception.

4. Signal and Channel for Time Index Indication

An SSB time index indication is delivered on the NR-PBCH. If the timeindex indication is included in a part of the NR-PBCH, such as NR-PBCHcontents, a scrambling sequence, a CRC, or a redundancy version, theindication is transmitted safely to the UE. However, if the time indexindication is included in the part of the NR-PBCH, the complexity ofdecoding of a neighbor cell NR-PBCH is added. Meanwhile, althoughdecoding of an NR-PBCH from a neighbor cell is possible, the decoding isnot mandatory in designing a system. Further, which signal and channelare suitable for delivering the SSB time index indication needsadditional discussion.

Because SSB time index information will be used as reference informationfor time resource allocation to an initial access-related channel/signalsuch as system information or a PRACH preamble in a target cell, the SSBtime index information should be transmitted safely to the UE.Meanwhile, a time index is used in RSRP measurement at an SSB level, forthe purpose of neighbor cell measurement. In this case, there may be noneed for very accurate SSB time index information.

In the present disclosure, it is proposed that an NR-PBCH DMRS is usedas a signal carrying an SSB time index. Further, it is proposed that atime index indication is included in a part of the NR-PBCH. The part ofthe NR-PBCH may be, for example, the scrambling sequence, the redundancyversion, or the like of the NR-PBCH.

According to the present disclosure, an SSB time index may be detectedfrom the NR-PBCH DMRS, and the detected index may be identified byNR-PBCH decoding. Further, an index may be acquired from an NR-PBCH DMRSof a neighbor cell, for the purpose of neighbor cell measurement.

The time index indication may be configured in the following twoembodiments.

(Method 1) A single index method in which every SSB in an SS burst setis indexed.

(Method 2) A multi-index method in which an index is assigned by acombination of an SS burst index and an SSB index.

If a single index method such as Method 1 is supported, a large numberof bits are required to represent all SSBs within an SS burst setperiod. In this case, the DMRS sequence and scrambling sequence of theNR-PBCH preferably indicate an SSB indication.

On the other hand, if a multi-index method such as Method 2 is used,design flexibility for the index indication may be provided. Forexample, both an SS burst index and an SSB index may be included in asingle channel. Further, each index may be transmitted individually in adifferent channel/signal. For example, an SS burst index may be includedin the contents or scrambling sequence of the NR-PBCH, whereas an SSBindex may be delivered in the DMRS sequence of the NR-PBCH.

Meanwhile, the maximum number of SSBs in a configured SS burst ischanged according to a carrier frequency range. That is, the maximumnumber of SSBs is 8 in a frequency range at or below 6 GHz, and 64 in afrequency range between 6 GHz and 52.6 GHz.

Therefore, the number of bits required to indicate an SSB or the numberof states required to indicate an SSB may vary according to a carrierfrequency range. Accordingly, it may be considered to apply one ofMethod 1 and Method 2 according to a carrier frequency range. Forexample, the single index method may be applied at or below 6 GHs, andthe multi-index method may be used at or above 6 GHz.

To describe in more detail, an SSB time index may be determined by thePBCH DMRS in the frequency range at or below 6 GHz. In this case, up to8 states should be identified by the PBCH DMRS sequence. That is, 3 bitsare required for the SSB time index. Further, a 5 ms boundary (a halftime indicator) may be indicated by the PBCH DMRS sequence. In thiscase, a total of 16 states are required to indicate the DMRS-based SSBtime index and the 5 ms boundary. In other words, in addition to 3 bitsfor the SSB time index, 1 bit is additionally required to indicate the 5ms boundary. Further, there is no need for defining bits for an SSB timeindex in the PBCH contents, in the frequency range at or below 6 GHz.

Meanwhile, if the bits for indicating an SSB time index is transmittedin the NR-PBCH DMRS, decoding performance is better than in the PBCHcontents. Further, if an additional signal is defined to indicate theSSB time index, the additional signal incurs signaling overhead. Sincethe NR-PBCH DMRS is an already defined sequence in the NR system, theNR-PBCH DMRS does not cause additional signaling overhead, thuspreventing excessive signaling overhead.

Meanwhile, in the frequency range at or above 6 GHz, a part of the SSBtime index may be indicated by the PBCH DMRS, whereas the remaining partof the SSB time index may be indicated by the PBCH contents. Forexample, to indicate a total of 64 SSB indexes, SSBs may be grouped intoup 8 SSB groups in an SS burst set, each SSB group including up to 8SSBs. In this case, 3 bits for indicating an SSB group may be defined inthe PBCH contents, and an SSB time index within the SSB group may bedefined by the PBCH DMRS sequence. In addition, if a synchronizationnetwork may be assumed in the frequency range at or above 6 GHz in theNR system, there is no need for performing a PBCH decoding procedure toacquire an SS burst index from PBCH contents.

5. NR-PBCH Contents

It is expected that the payload size of a master information block (MIB)will be increased on the basis of a response LS from RAN2 in the NRsystem. The MIB payload size and NR-PBCH contents, expected in the NRsystem, are given as follows.

1) Payload: 64 bits (48-bit information, 16-bit CRC)

2) NR-PBCH contents:

-   -   At least a part of SFN/H-SFN    -   Information about configuration of common search space    -   Information about central frequency of NR carrier

After detecting a cell ID and symbol timing information, a UE mayacquire network access information from a PBCH including an SFN, a partof timing information, such as an SSB index and a half frame timing,information related to a common control channel, such as atime/frequency position, a bandwidth, bandwidth part information such asthe position of an SSB, and SS burst set information such as an SS burstset period and an actual transmitted SSB index.

Since the only limited time/frequency resources of 576 REs are occupiedby the PBCH, mandatory information should be included in the PBCH. Inaddition, if possible, to further include mandatory information oradditional information, an auxiliary signal such as a PBCH DMRS may beused.

(1) SFN (System Frame Number)

In NR, SFNs may be defined to distinguish 10-ms intervals. Further,indexes between 0 and 1023 may be introduced as the SFNs, similarly tothe LTE system. The indexes may be explicitly indicated by bits orimplicitly indicated.

In NR, a PBCH TTI is 80 ms and a minimum SS burst period is 5 ms.Therefore, up to 16 PBCHs may be transmitted, one per 80 ms, and adifferent scrambling sequence for each PBCH transmission may be appliedto encoded PBCH bits. The UE may detect a 10-ms interval similarly to anLTE PBCH decoding operation. In this case, eight SFN states may beindicated implicitly by a PBCH scrambling sequence, and 7 bits forindicating an SFN may be defined in PBCH contents.

(2) Timing Information Within Radio Frame

An SSB index may be explicitly indicated by the PBCH DMRS sequenceand/or bits included in the PBCH contents, according to a carrierfrequency range. For example, for the frequency band at or below 6 GHz,3 bits of the SSB index is delivered only by the PBCH DMRS sequence.Further, for the frequency band at or above 6 GHz, the three LSBs of theSSB index is delivered by the PBCH DMRS sequence, and the three MSBs ofthe SSB index is delivered by the PBCH contents. That is, up to 3 bitsfor an SSB index may be defined in the PBCH contents, only for afrequency range between 6 GHz and 52.6 GHz.

In addition, a half frame boundary may be indicated by the PBCH DMRSsequence. Particularly, in a frequency band at 3 GHz or below, it ismore effective to include a half frame indicator in the PBCH DMRS thanin the PBCH contents. That is, FDD is mainly used in the frequency bandat or below 3 GHz, and thus time asynchronization between SFs or slotsmay be large. Therefore, for more accurate time synchronization, thehalf frame indicator is preferably delivered in the PBCH DMRS havingbetter decoding performance than the PBCH contents.

On the contrary, in a frequency band above 3 GHz, TDD is mainly used andthus time asynchronization between subframes or slots is not much.Therefore, it may not matter much to deliver the half time indicator inthe PBCH contents.

Meanwhile, the half time indicator may be delivered in both of the PBCHDMRS and the PBCH contents.

(3) Number of OFDM Symbols Included in Slot

Regarding the number of OFDM symbols in a slot in a carrier frequencyrange at or below 6 GHz, a 7-OFDM symbol slot and a 14-OFDM symbol slotare considered in NR. If it is determined to support both types of slotsin the carrier frequency range at or below 6 GHz, a slot type indicationshould be defined to indicate time resources of a control resource set(CORESET).

(4) Information Identifying Absence of RMSI Corresponding to PBCH

In NR, an SSB may be used for operation measurement as well as forproviding network access information. Particularly, multiple SSBs may betransmitted for measurement, for a wideband CC operation.

However, it may not be necessary to deliver RMSI in every frequencyposition carrying an SSB. That is, the RMSI may be transmitted in aspecific frequency position, for efficiency of resource utilization. Inthis case, UEs, which perform an initial access procedure, may notdetermine whether RMSI is provided in a detected frequency position. Tosolve the problem, a bit field for identifying the absence of RMSIcorresponding to a PBCH in a detected frequency area may need to bedefined. Meanwhile, a method for identifying the absence of RMSIcorresponding to a PBCH without using the bit field should also beconsidered.

For this purpose, an SSB without RMSI is to be transmitted in afrequency position which is not defined by a frequency raster. In thiscase, since UEs performing the initial access procedure are not capableof detecting an SSB, the above problem may be overcome.

(5) SS Burst Set Periodicity and Actual Transmitted SS Block

For the purpose of measurement, information about the periodicity of anSS burst set and an actual transmitted SSB may be indicated. Therefore,this information is preferably included in system information, for cellmeasurement and inter/intra cell measurement. That is, there is no needfor defining the above information in PBCH contents.

(6) Bandwidth-Related Information

A UE attempts to detect a signal within an SSB bandwidth during aninitial synchronization procedure including cell ID detection and PBCHdecoding. Subsequently, the UE may acquire system information in abandwidth indicated in PBCH contents by a network, and continue aninitial access procedure in which an RACH procedure is performed. Thebandwidth may be defined for the purpose of the initial accessprocedure. Frequency resources for a COCRESET, RMSI, OSI, and an RACHmessage may be defined within a bandwidth for a DL common channel. Inaddition, an SSB may be positioned in a part of the bandwidth for the DLcommon channel. In summary, the bandwidth for the DL common channel maybe defined in PBCH contents. Further, an indication of a relativefrequency position between the bandwidth for the SSB and the bandwidthfor the DL common channel may be defined in the PBCH contents. Tosimplify the indication of a relative frequency position, a plurality ofbandwidths for the SSB may be regarded as candidate positions in whichthe SSB is positioned within the bandwidth of the DL common channel.

(7) Numerology Information

For SSB transmission, the subcarrier spacings of 15, 30, 120, and 240kHz are used. Meanwhile, the subcarrier spacings of 15, 30, 60 and 120kHz are used for data transmission. For transmission of an SSB, aCORESET, and RMSI, the same subcarrier spacing may be used. Once RAN1identifies information about the above-described subcarrier spacings,there is no need for defining numerology information in PBCH contents.

Meanwhile, a probable change of the subcarrier spacing for the CORESETand the RMSI may be considered. If only 15 subcarrier spacings areapplied to SSB transmission according to an agreement on a minimumcarrier bandwidth in RAN4, the subcarrier spacing may need to be changedto 30 kHZ for the next procedure after PBCH decoding. Further, if the240-kHz subcarrier spacing is used for transmission of an SSB, thesubcarrier spacing needs to be changed for data transmission because the240-kHz subcarrier spacing is not defined for the data transmission. IfRAN1 is capable of changing the subcarrier spacing for data transmissionby PBCH contents, a 1-bit indicator may be defined for the purpose. The1-bit indicator may be interpreted as {15, 30 kHz} or {60, 120 kHz}according to a carrier frequency range. In addition, the indicatedsubcarrier spacing may be considered to be a default numerology for anRB grid.

(8) Payload Size

A maximum payload size of 64 bits may be assumed in consideration ofPBCH decoding performance, as illustrated in [Table 2].

TABLE 2 Bit size at or below at or above Details 6 GHz 6 GHz SystemFrame Number (MSB) 7 7 SS/PBCH block time index (MSB) 0 3 Referencenumerology [1] [1] Bandwidth for DL common channel, and SS [3] [2] blockposition # of OFDM symbols in a Slot [1] 0 CORESET About [10] About [10](Frequency resource - bandwidth, location) (Time resource - startingOFDM symbol, Duration) (UE Monitoring Periodicity, offset, duration)Reserved Bit [20]  [20]  CRS 16 + a 16 + a Total 64  64 

6. NR-PBCH Scrambling

A description will be given of the type of an NR-PBCH scramblingsequence and sequence initialization. Although it may be considered touse a PN sequence in NR, if use of a Gold sequence of length 31 definedin the LTE system as an NR-PBCH sequence does not cause a seriousproblem, it may be preferred to reuse the Gold sequence as an NR-PBCHscrambling sequence.

Further, the scrambling sequence may be initialized by at least aCell-ID, and 3 bits of an SSB index indicated by a PBCH-DMRS may be usedin initializing the scrambling sequence. Further, if a half frameindication is indicated by the PBCH-DMRS or another signal, the halfframe indication may also be used as a seed value for initialization ofthe scrambling sequence.

7. NR-PBCH DMRS Design

In the NR system, a DMRS is introduced for phase reference of theNR-PBCH. Further, an NR-PSS/NR-SSS/NR-PBCH exists in every SSB, and OFDMsymbols carrying the NR-PSS/NR-SSS/NR-PBCH are contiguous in a singleSSB. However, if it is assumed that the NR-SSS and the NR-PBCH aretransmitted in different transmission schemes, it cannot be assumed thatthe NR-SSS is used as an RS for NR-PBCH demodulation. In the NR system,therefore, the NR-PBCH should be designed on the assumption that theNR-SSS is not used as an RS for NR-PBCH demodulation.

To design a DMRS, DMRS overhead, a time/frequency position, and ascrambling sequence should be considered.

Overall PBCH decoding performance may be determined by channelestimation performance and an NR-PBCH coding rate. Because of tradeoffbetween channel estimation performance and a PBCH coding rate, anappropriate number of REs should be determined for DMRS transmission.For example, when four REs per RB are allocated to the DMRS, betterperformance may be provided. When two OFDM symbols are allocated forNR-PBCH transmission, 192 REs are used for the DMRS, and 384 REs areused for MIB transmission. In this case, on the assumption that thepayload size is 64 bits, a 1/12 coding speed equal to the coding speedof the LTE PBCH may be achieved.

In addition, if a plurality of OFDM symbols are allocated for NR-PBCHtransmission, which OFDM symbol is to include a DMRS becomes an issue.To prevent performance degradation caused by a residual frequencyoffset, the DMRS is preferably positioned in all OFDM symbols carryingthe NR-PBCH. Accordingly, the DMRS may be included in all OFDM symbolsused for NR-PBCH transmission.

Meanwhile, regarding the positions of OFDM symbols carrying the NR-PBCH,the PBCH DMRS is used as a time/frequency tracking RS, and as thespacing between two OFDM symbols carrying DMRSs is larger, frequencytracking is more accurate. Therefore, the first and fourth OFDM symbolsmay be allocated for transmission of the NR-PBCH.

Further, accordingly, interleaved mapping in the frequency domain may beassumed for the frequency position of the DMRS, which may be shiftedaccording to a cell ID. An advantage of a uniformly distributed DMRSpattern is that DFT-based channel estimation may be used, which offersoptimum performance in 1-D channel estimation. Further, in order toincrease channel estimation performance, wideband RB bundling may beused.

For a DMRS sequence, a pseudo random sequence defined according to thetype of a Gold sequence may be used. The length of the DMRS sequence maybe defined by the number of DMRS REs per SSB. In addition, the DMRSsequence may be generated on the basis of a Cell-ID and a slotnumber/OFDM symbol index within a default period 20 ms of an SS burstset. Further, the index of an SSB may be determined on the basis of slotand OFDM symbol indexes.

Meanwhile, NR-PBCH DMRSs should be scrambled according to 1008 cell IDsand 3-bit SSB indexes. This is because a comparison of detectionperformance according to numbers of hypotheses of a DMRS sequencereveals that the detection performance of 3 bits is most suitable forthe number of DMRS sequence hypotheses. However, since it seems that thedetection performance of 4 to 5 bits has little performance loss, itdoes not matter to use a 4- or 5-bit hypothesis number.

Meanwhile, since an SSB time index and a 5-ms boundary should berepresented by a DMRS sequence, a design should be made so that thereare a total of 16 hypotheses.

In other words, the DMRS sequence should represent at least a cell ID,an SSB index within an SS burst set, and a half frame boundary (halfframe indication), and may be initialized by the cell ID, the SSB indexwithin an SS burst set, and the half frame boundary (half frameindication). A specific initialization equation is given as [Equation1].c _(init)=(N _(ID) ^(SS/PBCH block)+1+8·HF)·(2·N _(ID) ^(cell)+1)·2¹⁰ N_(ID) ^(cell)  [Equation 1]

Herein, N_(ID) ^(SS/PBCHblock) represents an SSB index in an SSB group,and if N_(ID) ^(Cell) is a cell ID, HF represents a half frameindication index having a value of {0, 1}.

For the NR-PBCH DMRS sequence, a Gold sequence of length 31 may be used,similarly to the LTE DMRS sequence. Or the NR-PBCH DMRS sequence may begenerated based on a Gold sequence of length 7 or 8.

Meanwhile, since detection performance is similar in the cases of usinga Gold sequence of length 31 and a Gold sequence of length 7 or 8, thepresent disclosure proposes that the Gold sequence of length 31 is used,like the LTE DMRS, and a Gold sequence of a length larger than 31 may beconsidered in the frequency range at or above 6 GHz.

A DMRS sequence modulated in QPSK, r_(N) _(ID) _(SS/PBCH block) (m) maybe defined by [Equation 2].

$\begin{matrix}{{{r_{N_{ID}^{{SS}\text{/}{PBCHblock}}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,143} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Further, BPSK and QPSK may be considered as a modulation scheme forgenerating the DMRS sequence. Although BPSK and QPSK are similar indetection performance, QPSK outperforms BPS in correlation performance.Thus, QPSK is more appropriate as a modulation scheme for generating theDMRS sequence.

Meanwhile, a pseudo random sequence used to generate the NR-PBCH DMRSsequence is defined as a Gold sequence of length 31, and a sequence c(n)of length M_(PN) is defined by the following [Equation 3].c(n)=(x ₁(n±N _(C))+x ₂(n+N _(C)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 3]

Herein, n=0, 1, . . . , M_(PN)−1 and N_(C)=1600. The first m-sequencehas an initial value, x₁(0)=1, x₁(n)=0, n=1, 2, . . . , 30, and thesecond m-sequence has an initial value defined by

${c_{init} = {{\sum\limits_{i = 0}^{30}\;{{{x_{2}(i)} \cdot 2^{i}}\mspace{14mu}{where}\mspace{14mu}{x_{2}(i)}}} = {\left\lfloor \frac{c_{init}}{2^{i}} \right\rfloor\mspace{14mu}{mod}\mspace{14mu} 2}}},{i = 0},1,\ldots\;,30$

8. NR-PBCH DMRS Pattern Design

Regarding the frequency position of the DMRS, two DMRS RE mappingmethods may be considered. A fixing RE mapping method fixes an RSmapping area in the frequency domain, whereas a variable RE mappingmethod shifts an RS position according to a cell ID by a Vshift method.The variable RE mapping method advantageously randomizes interferenceand thus achieves an additional performance gain. Thus, it seems to bemore preferable to use the variable RE mapping method.

The variable RE mapping will be described in detail. A complexmodulation symbol a_(k,l) included in a half frame may be determined by[Equation 4].

$\begin{matrix}{{a_{k,l} = {r_{N_{ID}^{{SS}\text{/}{PBCHblock}}}\left( {{72 \cdot l^{\prime}} + m^{\prime}} \right)}}{k = {{{4m^{\prime}} + {v_{shift}\mspace{14mu}{if}\mspace{14mu} l}} \in \left\{ {1,3} \right\}}}l = \left\{ {{{\begin{matrix}1 & {l^{\prime} = 0} \\3 & {l^{\prime} = 1}\end{matrix}m^{\prime}} = 0},1,\ldots\;,{{71v_{shift}} = {N_{ID}^{cell}\mspace{14mu}{mod}\mspace{14mu} 3}}} \right.} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Herein, k and l represent the indexes of a subcarrier and an OFDM symbolin an SSB, and r_(N) _(ID) _(SS/PBCH block) (m) represents a DMRSsequence. Meanwhile, it may be determined by V_(shift)=N_(ID) ^(cell)mod 4.

Further, RS power boosting may be considered to improve performance. IfRS power boosting and Vshift are used together, interference frominterference total radiated power (TRP) may be reduced. Further,considering the detection performance gain of RS power boosting, theratio of signal EPRE to PDSCH EPRE is preferably −1.25 dB.

Meanwhile, DMRS overhead, a time/frequency position, and a scramblingsequence should be determined to design a DMRS. Overall PBCH decodingperformance may be determined by channel estimation performance and anNR-PBCH coding rate. Due to trade-off between channel estimationperformance and a PBCH coding rate, an appropriate number of REs for theDMRS should be determined.

It can be seen from a test that allocation of 4 REs per RB (⅓ density)to the DMRS offers better performance. If two OFDM symbols are used fortransmission of the NR-PBCH, 192 REs are used for the DMRS, and 384 REsare used for MIB transmission. In this case, on the assumption that thepayload size is 64 bits, the same coding speed as the LTE PBCH, that is,1/12 coding speed may be achieved.

Further, the DMRS may be used for a phase reference of the NR-PBCH.Herein, two methods may be considered for DMRS mapping. One of themethods is equidistant mapping in which each PBCH symbol is used, and aDMRS sequence is mapped to subcarriers at the same interval.

In a non-equidistant mapping scheme, each PBCH symbol is used, but aDMRS sequence is not mapped within an NR-SSS transmission bandwidth.Instead, the NR-SSS is used for PBCH demodulation in the non-equidistantmapping scheme. Therefore, the non-equidistant mapping scheme mayrequire more resources for channel estimation than the equidistantmapping scheme. In addition, since a residual CFO may exist in theinitial access procedure, SSS symbol-based channel estimation may not beaccurate. That is, the equidistant mapping scheme is advantageous in CFOestimation and accurate time tracking.

Further, if an SSB time indication is transmitted in the PBCH DMRS, theequidistant mapping scheme may bring an additional benefit. The resultsof evaluating PBCH decoding performance according to the actual REmapping scheme tell that the equidistant mapping scheme outperforms thenon-equidistant mapping scheme. Accordingly, the equidistant mappingscheme is more suitable for the initial access procedure. Further,regarding the frequency position of a DMRS, interleaved DMRS mapping inthe frequency domain, which may be shifted according to a cell ID, maybe assumed. In addition, the equidistantly mapped DMRS pattern maypreferably use DFT-based channel estimation which offers optimumperformance in 1-D channel estimation.

9. Time Index Indication Method

Referring to FIG. 15, time information includes an SFN, a half frameinterval, and an SSB time index. Regarding each piece of timeinformation, an SFN may be represented in 10 bits, a half frameindication may be represented in 1 bit, and an SSB time index may berepresented in 6 bits. Herein, a part of the 10 bits of the SFN may beincluded in PBCH contents. Further, an NR-PBCH DMRS may include 3 bitsout of the 6 bits of the SSB index.

Embodiments of a method for indicating a time index as illustrated inFIG. 15 may be given as follows.

-   -   Method 1: S2 S1 (PBCH scrambling)+S0 C0 (PBCH contents)    -   Method 2: S2 S1 S0 (PBCH scrambling)+C0 (PBCH contents)    -   Method 3: S2 S1 (PBCH scrambling)+S0 C0 (PBCH DMRS)    -   Method 4: S2 S1 S0 (PBCH scrambling)+C0 (PBCH DMRS)

If a half frame indication is delivered in the NR-PBCH DMRS, PBCH datamay be combined, thereby achieving additional performance improvement.For this reason, a 1-bit half frame indication may be transmitted in theNR-PBCH DMRS as in Method 3 and Method 4.

In a comparison between Method 3 and Method 4, although Method 3 mayreduce the number of blind decodings, Method 3 may lead to loss of PBCHDMRS performance. If the PBCH DMRS may deliver 5 bits including S0, C0,B0, B1, and B2 with excellent performance, Method 3 may be appropriateas a time indication method. However, if the PBCH DMRS may not deliverthe 5 bits with excellent performance, Embodiment 4 may be appropriateas a time indication method.

In consideration of the above, 7 MSBs of an SFN may be included in thePBCH contents, and 2 or 3 LSBs of the SFN may be delivered by PBCHscrambling. Further, 3 LSBs of an SSB index may be included in the PBCHDMRS, and 3 MSBs of the SSB index may be included in the PBCH contents.

Additionally, a method for acquiring an SSB time index of a neighborcell may be considered. Since DMRS sequence-based decoding outperformsPBCH contents-based decoding, 3 bits of an SSB index may be transmittedby changing a DMRS sequence within each 5-ms period.

Meanwhile, while an SSB time index may be transmitted only in an NR-PBCHDMRS of a neighbor cell in the frequency range at or below 6 GHz, 64 SSBindexes are distinguished by a PBCH-DMRS and PBCH contents in thefrequency range at or above 6 GHz, and thus a UE does not need to decodea PBCH of the neighbor cell.

However, decoding of the PBCH-DMRS and the PBCH contents together mayresult in additional complexity of NR-PBCH decoding, and reduced PBCHdecoding performance, compared to use of the PBCH-DMRS only.Accordingly, it may be difficult to perform PBCH decoding to receive anSSB of the neighbor cell.

In this context, it may be considered that a serving cell provides aconfiguration related to an SSB index of a neighbor cell, instead ofdecoding the PBCH of the neighbor cell. For example, the serving cellprovides a configuration for 3 MSBs of an SSB index of a target neighborcell, and the UE detects 3 LSBs from a PBCH-DMRS. Then, the SSB index ofthe target neighbor cell may be acquired by combining the 3 MSBs withthe 3 LSBs.

10. Measurement Result Evaluation

Now, a description will be given of the results of performancemeasurement according to a payload size, a transmission scheme, and aDMRS. It is assumed that two OFDM symbols having 24 RBs are used forNR-PBCH transmission. It is also assumed that an SS burst set (i.e., 10,20, 40, or 80 ms) may have a plurality of periods, and encoded bits aretransmitted within 80 ms.

(3) DMRS Density

In a low SNR area, improvement of channel estimation performance is asignificant factor in improving demodulation performance. However, ifthe RS density of the NR-PBCH increases, the channel estimationperformance is improved, but the coding speed is reduced. Therefore, forbalancing between the channel estimation performance and the channelcoding gain, decoding performance for different DMRS densities iscompared. FIG. 16 is an exemplary view illustrating DMRS densities.

FIG. 16(a) illustrates use of 2 REs per symbol for the DMRS, FIG. 16(b)illustrates use of 4 REs per symbol for the DMRS, and FIG. 16(c)illustrates use of 6 REs per symbol for the DMRS. In addition, thepresent evaluation is based on the assumption of using a singleport-based transmission scheme (i.e., TD-PVS).

FIG. 16 illustrates embodiments of a DMRS pattern for single antennaport-based transmission. Referring to FIG. 16, with the positions ofDMRSs equally distant from each other in the frequency domain, the RSdensity is changed. Further, FIG. 17 is a view illustrating performanceresults for the different DMRS densities.

As illustrated in FIG. 17, the NR-PBCH decoding performance in the caseillustrated in FIG. 16(b) is better than in the case illustrated in FIG.16(a), due to excellent channel estimation performance. Meanwhile, thecase of FIG. 16(c) has the effect of a coding speed loss larger than thegain of channel estimation performance improvement, and thus has poorperformance, compared to the case of FIG. 16(b). For this reason, itseems most appropriate to design the DMRS with an RS density of 4 REsper symbol.

(4) DMRS Time Position and CFO Estimation

A description will be given of the detection performance of an SSB indexaccording to the number of DMRS sequence hypotheses, a modulation type,sequence generation, and DMRS RE mapping. The present measurementresults are based on the assumption that two OFDM symbols in 24 RBs areused for NR-PBCH transmission. In addition, multiple periods may beconsidered for an SS burst set, and may be 10 ms, 20 ms, or 40 ms.

(5) Number of DMRS Sequence Hypotheses

FIG. 18 illustrates measurement results according to SSB indexes. 144REs and 432 REs are used for the DMRS and data, respectively in 24 RBsand two OFDM symbols. It is assumed that a long sequence (e.g., a Goldsequence of length 31) and QPSK are used for a DMRS sequence.

Referring to FIG. 18, when measurement is performed with the detectionperformance of 3 to 5 bits accumulated twice, an error rate of 1% isshown at −6 dB. Therefore, information of 3 to 5 bits may be used torepresent the number of hypotheses for a DMRS sequence in terms ofdetection performance.

(6) Modulation Type

FIGS. 19 and 20 illustrate the results of performance measurement inBPSK and QPSK. In the present test, a DMRS hypothesis is represented in3 bits, a DMRS sequence is based on a long sequence, and the power levelof an interference TRP is equal to the power level of a serving TRP.

Referring to FIGS. 19 and 20, it may be noted that BPSK and QPSK aresimilar in performance. Therefore, use of any modulation type formodulation of a DMRS sequence does not bring much difference in terms ofperformance measurement. However, referring to FIG. 21, it may be notedthat BPSK and QPSK differ in correlation characteristics.

Referring to FIG. 21, BPSK is more distributed than QPSK, in an areawith a correlation amplitude equal to or larger than 0.1. Accordingly,QPSK is preferably used as a modulation type for the DMRS inconsideration of a multi-cell environment. That is, QPSK is a moreappropriate modulation type for the DMRS sequence, in terms ofcorrelation characteristics.

(7) Generation of PBCH DMRS Sequence

FIGS. 22 and 23 illustrate measurement results according to DMRSsequence generation. A DMRS sequence may be generated on the basis of along sequence with a polynomial order of 30 or higher, or a shortsequence of a polynomial order of 8 or less. In addition, it is assumedthat a DMRS hypothesis is 3 bits, and the power level of an interferenceTRP is equal to that of a serving TRP.

Referring to FIGS. 22 and 23, it may be noted that the detectionperformance of short sequence-based generation is similar to thedetection performance of long sequence-based generation.

Specifically, although the correlation performance of a first M-sequenceis intended to be increased by introducing a polynomial expression oflength 7, no difference is made from conventional use of a length−31polynomial expression for a first M-sequence. In addition, while asequence is generated by setting the initial value of the firstM-sequence to an SSBID, it does not make any difference from aconventional scheme of fixing the first M-sequence and using anSSBID-CellID for the second M-sequence.

Accordingly, a length−31 Gold sequence is used as in LTE, andinitialization is performed by fixing the initial value of the firstM-sequence and using SSBID-CellID for the second M-sequence, as is doneconventionally.

(8) DMRS RE Mapping

FIGS. 24, 25 and 26 illustrate the results of performance measurementaccording to the equidistant RE mapping method and the non-equidistantRE mapping method. Herein, a DMRS hypothesis is 3 bits, a DMRS sequenceis based on a long sequence, and the power level of an interference TRPis equal to that of a serving TRP. In addition, only one interferencesource exists.

Further, the NR-SSS is mapped to 144 REs (i.e., 12 RBs), and the NR-PBCHis mapped to 288 REs (i.e., 24 RBs). Meanwhile, in the non-equidistantmapping method, it is assumed that the NR-SSS is used for PBCHdemodulation, and the PBCH DMRS is not mapped within an NR-SSStransmission bandwidth. Further, it is assumed that a residual CFOexists.

That is, the above-described contents are summarized as follows.

(Equidistant DMRS mapping) 96 REs per PBCH symbol, that is, a total of192 REs are used.

(Non-equidistant DMRS mapping) a DMRS sequence is mapped to subcarriersoutside the NR-SSS transmission bandwidth. In this case, the NR-SSS isused for PBCH demodulation. In addition, 48 REs per PBCH symbol, and 128REs for the NR-SSS symbol, that is, a total of 224 REs are used.

As noted from FIG. 25, the non-equidistant mapping scheme without a CFOincludes more REs for channel estimation, thus outperforming theequidistant mapping scheme. However, if 10% of a residual CFO exists,the performance of the non-equidistant mapping scheme decreases, whereasthe equidistant mapping scheme exhibits a similar performanceirrespective of a CFO. Even though the non-equidistant mapping schemehas more REs for channel estimation, the channel estimation accuracy ofthe NR-SSS symbol is decreased due to the residual CFO. Therefore, itmay be noted that in the presence of a residual CFO, the equidistantmapping scheme outperforms the non-equidistant mapping scheme in channelestimation performance.

As noted from FIG. 26, the use of variable RE mapping may bring aboutthe effect of interference randomization. Therefore, the detectionperformance of variable RE mapping is higher than that of fixed REmapping.

FIG. 27 illustrates measurement results when RS power boosting is used.Herein, it is assumed that the RE transmission power for a DMRS ishigher than the RE transmission power for PBCH data by about 1.76 dB(=10 log(1.334/0.889)). If variable RE mapping and DMRS power boostingare used together, other cell interference is reduced. As noted fromFIG. 27, there is a performance gain of 2 to 3 dB with RS powerboosting, compared to the absence of RS power boosting.

On the other hand, the RS power boosting reduces the RE transmissionpower for PBCH data. Thus, the RS power boosting may affect PBCHperformance. FIGS. 28 and 29 illustrate the results of measuring PBCHperformance in the cases of RS power boosting and no RS power boosting.It is assumed that the period of an SS burst set is 40 ms and encodedbits are transmitted within 80 ms.

The reduction of the RE transmission power for PBCH data may causeperformance loss. However, the resulting RS power increase improveschannel estimation performance, thereby improving demodulationperformance. Accordingly, as noted from FIGS. 28 and 29, the performanceis almost the same in both cases. Accordingly, the effect of the loss ofthe RE transmission power for PBCH data may be compensated for by achannel estimation performance gain.

[Table 3] below lists assumed values for parameters used for the aboveperformance measurement.

TABLE 3 Parameter Value Carrier Frequency 4 GHz Channel Model CDL_C(delay scaling values: 100 ns) Subcarrier Spacing 15 kHz AntennaConfiguration TRP: (1, 1, 2) with Omni-directional antenna element UE:(1, 1, 2) with Omni-directional antenna element Frequency Offset 0% and10% of subcarrier spacing Default period 20 ms Subframe duration 1 msOFDM symbols in SF 14  Number of interfering 1 TRPs Operating SNR −6 dB

(9) SSB Index Indication

Evaluation results for comparing the performance of an SSB time indexindication will be described with reference to FIGS. 30 to 33. For thepresent evaluation, a method for indicating an SSB time index by a PBCHDMRS sequence, and a method for indicating an SSB index by PBCH contentsare considered. It is assumed that for an SSB time index and 5-ms slotboundary indication, there are a total of 16 states, that is, theindication is represented in 4 bits. In this evaluation, it is assumedthat a single SSB of an SS burst set is transmitted, and time-domainprecoder cycling is applied within a PBCH TTI. In addition, it isassumed that 192 REs are used for the PBCH DMRS, and the bit size of anMIB including a CRC is 64 bits.

The number of hypotheses is 16 for this evaluation. This is because 4bits are required to represent 8 states for an SSB index and states fora 5 ms boundary in the PBCH DMRS. As noted from FIGS. 30 and 31, thedetection performance of an SSB time index in the PBCH DMRS reaches 0.2%at an SNR of −6 dB, when accumulated twice. As observed from thisevaluation, it is more preferable to use the PBCH DMRS in indicating anSSB index and a 5 ms boundary.

On the other hand, as noted from FIGS. 32 and 33, even though decodingis performed with accumulation twice, a PBCH FER of 1% cannot beachieved at the SNR of −6 dB. Therefore, if an SSB time index is definedonly in PBCH contents, the detection performance of the SSB time indexmay not be sufficient.

[Table 4] below lists parameter values assumed for the above evaluationof an SSB index indication.

TABLE 4 Parameter Value Carrier Frequency 2 GHz Channel Model CDL_C(delay scaling raises: 300 ns) System Bandwidth 24 RBs Number of OFDMsymbol 2 symbols for PBCH REs for DMRS and Data 192 (96 × 2) for DMRS,384 (192 × 2) for Data Payload size 72 bits, 64 bits, 56 bits, 48 bitsPBCH TTI 80 ms SS burst set periodicity 20 ms PBCH Repetition 4 timeswithin PBCH TTI Subcarrier Spacing 15 kHz Antenna Configuration 2Tx &2Rx Transmission Scheme Time Domain Precoder Vector Switching (TD-PVS)Channel Estimation Non-ideal Modulation Order QPSK Coding Scheme TBCC

11. BWP (Bandwidth Part) for DL Common Channel Transmission

The initial access procedure of LTE is performed within a systembandwidth configured by an MIB. Further, the PSS/SSS/PBCH is alignedwith respect to the center of the system bandwidth. A common searchspace is defined within the system bandwidth, system information isdelivered on a PDSCH in the common search space allocated within thesystem bandwidth, and an RACH procedure for Msg 1/2/3/4 is performed.

Meanwhile, while the NR system supports an operation within a widebandcomponent carrier (CC), it is very difficult in terms of cost toconfigure a UE to have the capability of performing a necessaryoperation within all wideband CCs. Accordingly, it may be difficult toimplement a reliable initial access procedure within a system bandwidth.

To avert this problem, a BWP may be defined for an initial accessprocedure in NR, as illustrated in FIG. 34. In the NR system, an initialaccess procedure for SSB transmission, system information delivery,paging, and an RACH procedure may be performed within a BWPcorresponding to each UE. Further, at least one DL BWP may include oneCORESET having a common search space in at least one primary CC.

Thus, DL control information related to at least RMSI, OSI, paging, andRACH message 2/4 may be transmitted in a CORESET having a common searchspace, and a DL data channel related to the DL control information maybe allocated within a DL BWP. Further, the UE may expect that an SSBwill be transmitted in a BWP corresponding to the UE.

That is, at least one DL BWP may be used for transmission of a DL commonchannel in NR. Herein, an SSB, a CORESET and RMSI with a common searchspace, OSI, paging, and a PDSCH for RACH Msg 2/4 may be included in theDL common channel. The RMSI may be interpreted as system informationblock 1 (SIB 1), which is system information that the UE should acquireafter receiving an MIB on a PBCH.

(1) Numerology

In NR, the subcarrier spacings of 15, 30, 60 and 120 kHz are used fordata transmission. Therefore, a numerology for a PDCCH and a PDSCHwithin an BWP for a DL common channel may be selected from amongnumerologies defined for data transmission. For example, one or more ofthe subcarrier spacings of 30, 60 and 60 kHz may be selected for afrequency range at or below 6 GHz, whereas one or more of the subcarrierspacings of 60 and 120 kHz may be selected for a frequency range of 6GHz to 52.6 kHz.

However, since the 60-kHz subcarrier spacing is already defined forURLLC service in the frequency range at or below 6 GHz, the 60-kHzsubcarrier spacing is not suitable for PBCH transmission in thefrequency range at or below 6 GHz. Accordingly, for transmission of a DLcommon channel, the subcarrier spacings of 15 kHz and 30 kHz may be usedin the frequency range at or below 6 GHz, and the subcarrier spacings of60 kHz and 120 kHz may be used in the frequency range at or above 6 GHz.

Meanwhile, the subcarrier spacings of 15, 30, 120 and 240 kHz aresupported for SSB transmission in NR. It may be assumed that the samesubcarrier spacing is applied to downlink channels for an SSB, a CORESETand RMSI with a common search space, paging, and a PDSCH for an RAR.Therefore, if this assumption is applied, there is no need for definingnumerology information in PBCH contents.

On the other hand, it may occur that a subcarrier spacing for a DLcontrol channel needs to be changed. For example, if the 240-kHzsubcarrier spacing is applied to SSB transmission in the frequency bandat or above 6 GHz, the 240-kHz subcarrier spacing is not used for datatransmission including DL control channel transmission, and thus thesubcarrier spacing needs to be changed for data transmission includingDL control channel transmission. Thus, if the subcarrier spacing can bechanged for data transmission including DL control channel transmission,this may be indicated by a 1-bit indicator included in the PBCHcontents. For example, the 1-bit indicator may be interpreted asindicating {15 kHz, 30 kHz} or {60 kHz, 120 kHz} according to a carrierfrequency range. In addition, the indicated subcarrier spacing may beregarded as a reference numerology for an RB grid. The PBCH contents maymean an MIB transmitted on the PBCH.

That is, in the frequency range at or below 6 GHz, the 1-bit indicatormay indicate that the subcarrier spacing for RMSI or OSI, paging, andMsg 2/4 for initial access is 15 kHz or 30 kHz, whereas in the frequencyrange at or above 6 GHz, the 1-bit indicator may indicate that thesubcarrier spacing for RMSI or OSI, paging, and Msg 2/4 for initialaccess is 60 kHz or 120 kHz.

(2) Bandwidth of BWP for Transmission of DL Common Channel

In the NR system, the bandwidth of a BWP for a DL common channel doesnot need to be equal to a system bandwidth in which the networkoperates. That is, the bandwidth of the BWP may be narrower than thesystem bandwidth. That is, although the bandwidth should be wider than aminimum carrier bandwidth, the bandwidth should not be wider than aminimum UE bandwidth.

Therefore, a BWP for transmission of a DL common channel may be definedsuch that the bandwidth of the BWP is wider than the bandwidth of anSSB, and equal to or less than a specific DL bandwidth of every UEoperable in each frequency range. For example, the minimum carrierbandwidth may be defined as 5 MHz and the minimum UE bandwidth may beassumed to be 20 MHz in the frequency range at or below 6 GHz. In thiscase, the bandwidth of the DL common channel may be defined in a rangeof 5 MHz to 20 MHz. That is, an SSB may be located in a part of thebandwidth of the DL common channel.

(3) Bandwidth Configuration

FIG. 35 illustrates an exemplary bandwidth configuration.

The UE attempts to detect a signal within the bandwidth of an SSB in aninitial synchronization procedure including cell ID detection and PBCHdecoding. Then, the UE may continue a subsequent initial accessprocedure within the bandwidth of a DL common channel, indicated by thenetwork in PBCH contents. That is, the UE may acquire system informationwithin the bandwidth of the DL common channel, and perform an RACHprocedure.

Meanwhile, an indicator indicating a relative frequency position betweenthe bandwidth of the SSB and the bandwidth of the DL common channel maybe defined in the PBCH contents. Meanwhile, as described above, the PBCHcontents may mean an MIB transmitted on the PBCH. For example, asillustrated in FIG. 35, the relative frequency position between thebandwidth of the DL common channel and the bandwidth of the SSB may bedefined by offset information about the spacing between the bandwidth ofthe SSB and the bandwidth of the DL common channel.

Particularly, referring to FIG. 35, the offset value may be indicated inRBs, and the UE may determine that the bandwidth of the DL commonchannel is located at an offset position corresponding to an indicatednumber of RBs. Meanwhile, different numerologies, that is, differentsubcarrier spacings may be configured for the bandwidth of the SSB andthe bandwidth of the DL common channel. Herein, the absolute frequencyspacing of an offset indicated in RBs may be calculated with respect toeither of the subcarrier spacing for the SSB bandwidth and thesubcarrier spacing for the bandwidth of the DL common channel.

Further, to simplify the indication of a relative frequency position, abandwidth for a plurality of SSBs may be one of candidate positions foran SSB within the bandwidth of the DL common channel.

Further, the bandwidth of the DL common channel does not need to beequal to the system bandwidth in which the network operates in the NRsystem. In addition, the bandwidth may be narrower than the systembandwidth. That is, although the bandwidth of the DL common channelshould be wider than the minimum carrier bandwidth, it should not bewider than the minimum bandwidth of the UE. For example, if it isassumed that in the frequency range at or below 6 GHz, the minimumcarrier bandwidth is defined as 5 MHz and the minimum bandwidth of theUE is assumed to be 20 MHz, the bandwidth of the DL common channel maybe defined within a range of 5 MHz to 20 MHz.

For example, if the bandwidth of an SSB is 5 MHz and the bandwidth ofthe DL common channel is 20 MHz, four candidate positions in which anSSB is to be detected may be defined within the bandwidth of the DLcommon channel.

12. CORESET Configuration

(1) CORESET Information and RMSI Scheduling Information

It may be more efficient for the network to transmit CORESET informationincluding RMSI scheduling information to the UE than to directlyindicate the RMSI scheduling information. That is, frequencyresource-related information such as a bandwidth for a CORESET and afrequency position may be indicated in PBCH contents. Further, timeresource-related information such as a starting OFDM symbol, a duration,and the number of OFDM symbols may be additionally configured in orderto flexibly use network resources.

In addition, information about a period, a duration, and an offset forcommon search space monitoring may be transmitted to the UE by thenetwork in order to reduce the detection complexity of the UE.

Meanwhile, a transmission type and an REG bundling size may be fixedaccording to the CORESET of a common search space. Herein, transmissiontypes may be classified depending on whether a transmitted signal isinterleaved.

(2) Number of OFDM Symbols Included in Slot

In relation to the number of OFDM symbols in a slot or a carrierfrequency range at or below 6 GHz, two candidates, that is, 7-OFDMsymbol slot and 14-OFDM symbol slot are considered. If it is determinedin the NR system to support the two types of slots in the carrierfrequency range at or below 6 GHz, a method for indicating a slot typeshould be defined in order to indicate the time resources of a CORESETwith a common search space.

(3) Bit Size of PBCH Contents

About 14 bits may be set to represent a numerology, a bandwidth, andCORESET information in PBCH contents.

TABLE 5 Bit size Details 6 GHz For a6 GHz Reference numerology [1] [1]Bandwidth for DL common channel, and SS [3] [2] block position # of OFDMsymbols in a Slot [1] 0 CORESET About [10] About [10] (Frequencyresource - bandwidth, location) (Time resource - starting OFDM symbol,Duration) (UE Monitoring Periodicity, offset, duration) Total About [14]

(4) Measurement Result

With reference to FIG. 36, performance results according to payloadsizes (i.e., 48, 56, 64, and 72 bits) will be described. Herein, it isassumed that 384 REs and 192 REs are used for DMRSs.

It may be noted from FIG. 36 that if the payload size is up to 72 bits,performance requirements for the NR-PBCH (i.e., 1% BLER at an SNR of −6dB) may be satisfied by using 384 REs for data and 192 REs for DMRSs.

FIG. 37 is a block diagram illustrating components of a transmittingdevice 10 and a receiving device 20 which implement the presentdisclosure.

The transmitting device 10 and the receiving device 20, respectivelyinclude radio frequency (RF) units 13 and 23 which transmit or receiveradio signals carrying information/and or data, signals, and messages,memories 12 and 22 which store various types of information related tocommunication in a wireless communication system, and processors 11 and21 which are operatively coupled with components such as the RF units 13and 23 and the memories 12 and 22, and control the memories 12 and 22and/or the RF units 13 and 23 to perform at least one of the foregoingembodiments of the present disclosure.

The memories 12 and 22 may store programs for processing and control ofthe processors 11 and 21, and temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally provide overall control to theoperations of various modules in the transmitting device or thereceiving device. Particularly, the processors 11 and 21 may executevarious control functions to implement the present disclosure. Theprocessors 11 and 21 may be called controllers, microcontrollers,microprocessors, microcomputers, and so on. The processors 11 and 21 maybe achieved by various means, for example, hardware, firmware, software,or a combination thereof. In a hardware configuration, the processors 11and 21 may be provided with application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), etc. In a firmware or software configuration,firmware or software may be configured to include a module, a procedure,a function, or the like. The firmware or software configured toimplement the present disclosure may be provided in the processors 11and 21, or may be stored in the memories 12 and 22 and executed by theprocessors 11 and 21.

The processor 11 of the transmitting device 10 performs a predeterminedcoding and modulation on a signal and/or data which is scheduled by theprocessor 11 or a scheduler connected to the processor 11 and will betransmitted to the outside, and then transmits the encoded and modulatedsignal and/or data to the RF unit 13. For example, the processor 11converts a transmission data stream to K layers after demultiplexing,channel encoding, scrambling, modulation, and so on. The encoded datastream is referred to as a codeword, equivalent to a data block providedby the MAC layer, that is, a transport block (TB). One TB is encoded toone codeword, and each codeword is transmitted in the form of one ormore layers to the receiving device. For frequency upconversion, the RFunit 13 may include an oscillator. The RF unit 13 may include N_(t)transmission antennas (N_(t) is a positive integer equal to or greaterthan 1).

The signal process of the receiving device 20 is configured to bereverse to the signal process of the transmitting device 10. The RF unit23 of the receiving device 20 receives a radio signal from thetransmitting device 10 under the control of the processor 21. The RFunit 23 may include N_(r) reception antennas, and recovers a signalreceived through each of the reception antennas to a baseband signal byfrequency downconversion. For the frequency downconversion, the RF unit23 may include an oscillator. The processor 21 may recover the originaldata that the transmitting device 10 intends to transmit by decoding anddemodulating radio signals received through the reception antennas.

Each of the RF units 13 and 23 may include one or more antennas. Theantennas transmit signals processed by the RF units 13 and 23 to theoutside, or receive radio signals from the outside and provide thereceived radio signals to the RF units 13 and 23 under the control ofthe processors 11 and 21 according to an embodiment of the presentdisclosure. An antenna may also be called an antenna port. Each antennamay correspond to one physical antenna or may be configured to be acombination of two or more physical antenna elements. A signaltransmitted from each antenna may not be further decomposed by thereceiving device 20. An RS transmitted in correspondence with acorresponding antenna defines an antenna viewed from the side of thereceiving device 20, and enables the receiving device 20 to performchannel estimation for the antenna, irrespective of whether a channel isa single radio channel from one physical antenna or a composite channelfrom a plurality of physical antenna elements including the antenna.That is, the antenna is defined such that a channel carrying a symbol onthe antenna may be derived from the channel carrying another symbol onthe same antenna. In the case of an RF unit supporting MIMO in whichdata is transmitted and received through a plurality of antennas, the RFunit may be connected to two or more antennas.

In the present disclosure, the RF units 13 and 23 may support receptionBF and transmission BF. For example, the RF units 13 and 23 may beconfigured to perform the exemplary functions described before withreference to FIGS. 5 to 8 in the present disclosure. In addition, the RFunits 13 and 23 may be referred to as transceivers.

In embodiments of the disclosure, a UE operates as the transmittingdevice 10 on UL, and as the receiving device 20 on DL. In theembodiments of the disclosure, the gNB operates as the receiving device20 on UL, and as the transmitting device 10 on DL. Hereinafter, aprocessor, an RF unit, and a memory in a UE are referred to as a UEprocessor, a UE RF unit, and a UE memory, respectively, and a processor,an RF unit, and a memory in a gNB are referred to as a gNB processor, agNB RF unit, and a gNB memory, respectively.

In the present disclosure, the gNB processor controls transmission of anSSB including a PSS/SSS/PBCH to a UE. A subcarrier spacing to be appliedto a DL common channel is indicated by a 1-bit indicator in an MIBtransmitted on the PBCH. The 1-bit indicator indicates that thesubcarrier spacing is 15 kHz or 30 kHz in a band below 6 GHz, and 60 kHzor 120 kHz in a band above 6 GHz. Further, the subcarrier spacingindicated by the 1-bit indicator is applied commonly to transmission ofRMSI, OSI, and MSg 2/4.

In the present disclosure, the UE processor controls reception of an SSBincluding a PSS/SSS/PBCH from a gNB. The UE processor receives asubcarrier spacing for a DL common channel by a 1-bit indicator in anMIB of the PBCH. The 1-bit indicator indicates that the subcarrierspacing is 15 kHz or 30 kHz in a band below 6 GHz, and 60 kHz or 120 kHzin a band above 6 GHz. Further, the subcarrier spacing indicated by the1-bit indicator is applied commonly to reception of RMSI, OSI, and MSg2/4.

The gNB processor or the UE processor of the present disclosure may beconfigured to implement the present disclosure in a cell operating in ahigh frequency band at or above 6 GHz in which analog BF or hybrid BF isused.

As described before, a detailed description has been given of preferredembodiments of the present disclosure so that those skilled in the artmay implement and perform the present disclosure. While reference hasbeen made above to the preferred embodiments of the present disclosure,those skilled in the art will understand that various modifications andalterations may be made to the present disclosure within the scope ofthe present disclosure. For example, those skilled in the art may usethe components described in the foregoing embodiments in combination.The above embodiments are therefore to be construed in all aspects asillustrative and not restrictive. The scope of the disclosure should bedetermined by the appended claims and their legal equivalents, not bythe above description, and all changes coming within the meaning andequivalency range of the appended claims are intended to be embracedtherein.

INDUSTRIAL APPLICABILITY

While the above-described method and apparatus for transmitting andreceiving a DL channel have been described in the context of the 5G NewRAT system, the method and apparatus are also applicable to variousother wireless communication systems than the 5G New RAT system.

The invention claimed is:
 1. A method for receiving a downlink (DL)common channel (CCH) by a user equipment (UE) operating in a frequencyband in a wireless communication system, the method comprising:receiving a synchronization signal block (SSB) including a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),and a physical broadcasting channel (PBCH); determining a subcarrierspacing for the DL CCH based on 1 bit information obtained via the PBCH;and receiving the DL CCH based on the subcarrier spacing, wherein thesubcarrier spacing is determined differently based on the frequencyband, wherein the DL CCH is for remaining minimum system information(RMSI) and DL messages for a random access, and wherein firstinformation related to a frequency resource configuration for the DLCCH, second information related to a time resource configuration of asymbol duration for the DL CCH and third information related tomonitoring of a common search space for the DL CCH are configured in thePBCH.
 2. The method according to claim 1, wherein based on the frequencyband exceeding a specific value, the subcarrier spacing is determined as60 kHz or 120 kHz.
 3. The method according to claim 1, wherein based onthe frequency band being below a specific value, the subcarrier spacingis determined as 15 kHz or 30 kHz.
 4. The method according to claim 1,wherein the 1 bit information is obtained independently from informationrelated to a subcarrier spacing for a DL channel except for the DL CCH.5. The method according to claim 1, wherein a subcarrier spacing for theRMSI and a subcarrier spacing for the DL messages for the random accessare same.
 6. A communication apparatus configured to operate in afrequency band for receiving a downlink (DL) common channel (CCH) in awireless communication system, the communication apparatus comprising: amemory; and a processor coupled to the memory and configured to: receivea synchronization signal block (SSB) including a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and a physicalbroadcasting channel (PBCH), determine a subcarrier spacing for the DLCCH based on 1 bit information obtained via the PBCH, and receive the DLCCH based on the subcarrier spacing, wherein the subcarrier spacing isdetermined differently based on the frequency band, wherein the DL CCHis for remaining minimum system information (RMSI) and DL messages for arandom access, and wherein first information related to a frequencyresource configuration for the DL CCH, second information related to atime resource configuration of a symbol duration for the DL CCH andthird information related to monitoring of a common search space for theDL CCH are configured in the PBCH.
 7. The communication apparatusaccording to claim 6, wherein based on the frequency band exceeding aspecific value, the subcarrier spacing is determined as 60 kHz or 120kHz.
 8. The communication apparatus according to claim 6, wherein basedon the frequency band being below a specific value, the subcarrierspacing is determined as 15 kHz or 30 kHz.
 9. The communicationapparatus according to claim 6, wherein the 1 bit information isobtained independently from information related to a subcarrier spacingfor a DL channel except for the DL CCH.
 10. The communication apparatusaccording to claim 6, wherein a subcarrier spacing for the RMSI and asubcarrier spacing for the DL messages for the random access are same.11. A method for transmitting a downlink (DL) common channel (CCH) by abase station (BS) supporting a frequency band in a wirelesscommunication system, the method comprising: transmitting asynchronization signal block (SSB) including a primary synchronizationsignal (PSS), a secondary synchronization signal (SSS), and a physicalbroadcasting channel (PBCH), wherein the PBCH includes 1 bit informationrelated to a subcarrier spacing for the DL CCH; and transmitting the DLCCH based on the 1 bit information, wherein the subcarrier spacing isdetermined differently based on the frequency band, wherein the DL CCHis for remaining minimum system information (RMSI) and DL messages for arandom access, and wherein first information related to a frequencyresource configuration for the DL CCH, second information related to atime resource configuration of a symbol duration for the DL CCH andthird information related to monitoring of a common search space for theDL CCH are configured in the PBCH.
 12. A communication apparatussupporting a frequency band for transmitting a downlink (DL) commonchannel (CCH) in a wireless communication system, the communicationapparatus comprising: a memory; and a processor coupled to the memoryand configured to: transmit a synchronization signal block (SSB)including a primary synchronization signal (PSS), a secondarysynchronization signal (SSS), and a physical broadcasting channel(PBCH), wherein the PBCH includes 1 bit information related to asubcarrier spacing for the DL CCH, and transmit the DL CCH based on 1bit information, wherein the subcarrier spacing is determineddifferently based on the frequency band, wherein the DL CCH is forremaining minimum system information (RMSI) and DL messages for a randomaccess, and wherein first information related to a frequency resourceconfiguration for the DL CCH, second information related to a timeresource configuration of a symbol duration for the DL CCH and thirdinformation related to monitoring of a common search space for the DLCCH are configured in the PBCH.